For some reason the developers have packed the DLL with UPX. This is what causes the problems with AVG (in my case).
Unpacking the dll is simple. Download UPX from
http://upx.sourceforge.net/download/upx303w.zip or go there directly to ensure that you get a clean file.
Unzip upx.exe to the C:\Program Files\PokerOffice\bin (again in my case - change as you see fit for your installation).
Go to Start -> Run and type "cmd" (without the quotes) and press return
Navigate to your installation directory (normally this is just "cd \Program Files\PokerOffice\bin" again without quotes) and type "upx -d injlib.dll". This will unpack the DLL into its original uncompressed form and for me prevents any false positives with AVG.
Hope this helps someone
bb