patch failing to apply?

[kestrel_80]

When I try to patch up to 3.27, I always get the following message:

dom3.exe: error - cannot replace, denied access

What I've tried so far:
* Re-installing, several times
* Tried different installation folder
* Tried different destination harddrive
* Running the patch file as administrator
* Disabling my anti-virus software

I get the same error message with the 3.26 patch, but the 3.24 patch does install correctly. The game always hangs after the first turn in v. 3.24 though...

My OS is Windows 7 Ultimate 64-bit, if that helps.

Is there anything else I can try? I'm dying to try the game, this is the first Dominions game that I've bought.