You only have this problem under Vista? Could you be more specific about the nature of the 'issues'?
Generally speaking about functions keys... A lot of host apps require custom mapped keys in order to work, not the default VT330 keys. It might be a good idea to find out what the host is *expecting* to see in terms of escape sequences and then map the Absolute keys to mimic that. If you have some other terminal app whose function keys *do* work, that would be a help in determining how to map the keys.
The current version of 7, btw is 7.14 if you want to try that...
http://www.celestialsoftware.net/telnet/AbsoluteTelnet7.14.exe
Brian