When migrating our TFS from a workgroup based install to Active Directory, we got a couple errors when running Team Build.
Access to the path 'C:\...BuildLog.txt' is denied
To fix this error, I simply deleted the root Team Project folders in Windows Explorer and re-ran the build. The build then recreated the folders. You may have to run the builds in a specific order if your solutions reference assemblies that live in these folders.
The other error occurred after a build started:
TF42004: Team Build failed to open folder \\server\share
To fix this error, I explicitly gave the new Active Directory user TFSService full control over the share permission for the folder that contains our drops. TFSService is the account that launches the build process. More details about this error are here.
These fixed the last of our problems (I think) with migrating to Active Directory. Part 1, Part 2 and Part 3 are also available for your reading enjoyment.