Just gave that a shot. When I go to the Master Keys tab of PGP Options and select the Add button, I see a key listed that states "Unknown Key, Key ID is 0xDBAA61E2." I added my key and then tried creating the new Netshare folder and got the same error...
One thing I do now notice is that when I go to PGP Desktop-All Keys, I see my key listed (along with the keys of other people I have previously given access to created Netshare folders), but the icon has only 1 key, which I believe should show 2 keys, representing both a public and private key. Any idea if this could be the issue, and if so, where did my other key go? I just tried to access a previously created Netshare folder and can not access it. This leads me to believe that possibly something is wrong with my private key. I have made no changes to PGP since I last created a Netshare folder.