Question : Difference/s between Cisco Callmanager 4.1(3)sr2 and 4.1(3)sr3a

Can anyone tell me the differences between these two versions? I'm aware that it will be mainly bugfixes etc.

Answer : Difference/s between Cisco Callmanager 4.1(3)sr2 and 4.1(3)sr3a

you're correct, primarily things like bug fixes. You can find some readme's and release notes that cover all the details, couple links:

http://www.spanlink.com/downloads/services/mtce/ciscocm.4-1-3-sr3a-Readme.htm

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/rel_notes/4_1/413cmrn.html