Thanks for your replies. The guide in your sig was very helpful as it made the gamespy browser a little easier to understand.
Incase anyone else is reading this and having similar problems with being unable to join games and being kicked back to the gamespy browser, try the following:
1. Create a folder in your arma2 directory called "battleye"
2. Goto http://www.battleye.com/download.html
3. download the client and server files under the arma 2 heading
4. place the downloaded files into the battleye folder created in step 1.
For some reason arma 2 did not install it or does not know where to look for it because since performing the instructions above I can now join most servers fine.