The only issue I've heard of with mixing the most recent SRAM and Shimano is that the derailleurs and shifters have to match because they use different indexing. That said, it sounds like you need to adjust the inner limit screw on the front derailleur. I'd suggest you check out:

http://www.parktool.com/repair_help/...railleur.shtml

I've only ever mucked about with the drivetrain on my bike once so you may want to get a 2nd opinion