I have an ASA5510 running 7.2(1)19 and ASDM 5.2(1). I have anyconnect-win-2.2.0133-k9.pkg installed, but 64bit clients cannot connect to it.
The 64bit clients log in and they float to a portal and the client is not downloaded. 32bit machines get the client downloaded.
The any-connect client requires ASA 8.x and not 7.2.x. Please have a look at this link:
I would say go for 8.0.3 (or the latest in this train).