1. One solution could be to download and execute the Intelligent Updater specific for you version of the product and OS.
     http://www.symantec.com/business/security_response/definitions/download/detail.jsp?gid=gw
2. Another solution would be to point your product to the previous version of definitions. This can be done by going into your Program Files\Common Files\Symantec Shared\VirusDefs folder and then editing your definfo.dat and usage.dat file. In the definfo.dat file there are two lines for definitions which start with CurDefs and LastDefs. Copy and paste everything to the right of the equal sign from the LastDefs line to the CurDefs line so that both lines are pointing to the previous set. Here is an example of the definfo.dat:
[DefDates]
CurDefs=20091203.004
LastDefs=20091202.024

and change that to look like this:
[DefDates]
CurDefs=20091202.024
LastDefs=20091202.024

Here is an example of the usage.dat file.
[20091203.004]
SMSDOM_8.0=1
SMSDOM_8.0_UPDATE=1

Your usage.dat may look different or have other Symantec products in there but the key here is to just look for the Domino product and then change the number in brackets above it to the same definitions number in the definfo.dat file. So I would change the above usage.dat file to look like the following:
[20091202.024]
SMSDOM_8.0=1
SMSDOM_8.0_UPDATE=1