Can you leave Verdistis by the main gate, or by teleporter stone? Doesn't sound like it.
Try deleting all of the files in the '
..\Divine Divinity\Run\Dynamic' folder. Then start Divinity, load the save and try leaving.
This folder is used as a cache for the game. Files are created / copied there from the save game folder when you load, and written / copied from that folder when you save a game. The files will be re-created as required the next time you start Divinity. If there was a corrupt file in that folder, deleting the files should fix the problem.
A possible work-around is
Teleporting Anywhere, via hex editor, but even if it works, the problem may re-occur the next time you try to enter/leave Verdistis (depending on what is causing the problem in the first place).
Do you have any recent saves you can re-load, to see if they also have this problem?
For the patch, it might help to try saving it to disk first, then run it. See this list of
freeware download managers.