After upgrading to 11.0.780.000 on my XP machine, my PPTP VPN connection failed. I kept getting error 633 every time I tried to connect. Shutting down ZA did not help but uninstalling ZA did.
After wasted time in Chat with three ZA support members and blaming my machine for the problem, I decided to re-install the earlier version which I still had. The VPN PPTP connection worked. Now that I have lost my ZA config which I have tuned for from a long time ago, I was free to re-install the new update. Sure enough the connection broke again.
After a lengthy debug session, it appears that it was the Kasparsky engine which is now part of ZA. It is unclear if it is the KAVSDK or the NDIS filter driver installed by ZA. The is a history of Kasparsky breaking PPTP connections and ZA should have known it.
Edit Note: It seems there was an existing thread regarding this issue which was apparently closed with no solution.