I have used the sylinkmonitor and the following line from the info it produces i think might be the problem.
6/08 10:20:05 [11820] <LUThreadProc>@@@@@@@@@ LU DEBUG ONLY- Download file failed due to wrong file size.
FileName:C:\Program Files (x86)\Symantec\Symantec Endpoint Protection\LiveUpdate\LUF{1CD85198-26C6-4bac-8C72-5D34B025DE35}1006070341.TMP Expected file size: 83151692
And
06/08 10:19:18 [4916] <GetIndexFileRequest:>RECEIVE STAGE COMPLETED
06/08 10:19:18 [4916] <GetIndexFileRequest:>COMPLETED
06/08 10:19:18 [4916] <IndexHeartbeatProc>GetIndexFile handling status: 0
06/08 10:19:18 [4916] <IndexHeartbeatProc>Switch Server flag=0
06/08 10:19:18 [4916] HEARTBEAT: Check Point 5.1
06/08 10:19:18 [4916] <IsInClientIPorOnLink> NextHop is equal to192.168.16.3,return TRUE
06/08 10:19:18 [4916] <mfn_GetOutIP> Out IP is:192.168.16.3
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=0
06/08 10:19:18 [4916] <mfn_LiveUpdate:> Agent returned closest matching seq: 100329018
06/08 10:19:18 [4916] <Add2LUFileList:>Adding LU Info to LU Download File List: {C60DC234-65F9-4674-94AE-62158EFCA433}100607034
06/08 10:19:18 [4916] <Add2LUFileList:>File Info already exists, hence updating: {C60DC234-65F9-4674-94AE-62158EFCA433}100607034
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {1CD85198-26C6-4bac-8C72-5D34B025DE35} Seq:100607034
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {42B17E5E-4E9D-4157-88CB-966FB4985928} Seq:100513001
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {D3769926-05B7-4ad1-9DCF-23051EEE78E3} Seq:100513001
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {C25CEA47-63E5-447b-8D95-C79CAE13FF79} Seq:80929016
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=20
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {EA960B33-2196-4d53-8AC4-D5043A5B6F9B} Seq:80820001
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=20
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {DB206823-FFD2-440a-9B89-CCFD45F3F1CD} Seq:80820001
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {C13726A9-8DF7-4583-9B39-105B7EBD55E2} Seq:80820001
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {CC40C428-1830-44ef-B8B2-920A0B761793} Seq:100607021
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {812CD25E-1049-4086-9DDD-A4FAE649FBDF} Seq:100607021
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {E1A6B4FF-6873-4200-B6F6-04C13BF38CF3} Seq:100607021
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_LU_REQUIRE_STATUS
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_LU_REQUIRE_STATUS, return=1
06/08 10:19:18 [4916] <mfn_LiveUpdate> EVENT_LU_REQUIRE_STATUS returned ERROR_SYSTEM_UNKNOWN - Ignore LU content. Moniker: {E5A3EBEE-D580-421e-86DF-54C0B3739522} Seq:100607021
06/08 10:19:18 [4916] <PostEvent>going to post event=EVENT_SERVER_ONLINE
06/08 10:19:18 [4916] <PostEvent>done post event=EVENT_SERVER_ONLINE, return=0
06/08 10:19:18 [4916] <ScheduleNextUpdate>Reset Heartbeat factor index, hearbeat=300 seconds
06/08 10:19:18 [4916] HEARTBEAT: Check Point 6