As WVSig said, almost all failures in a 1911 can be attributed to the magazines or the extractor tension. Here is a good test that many use to see if your extractor is tensioned properly
http://modernserviceweapons.com/?p=131
Also, I would buy some quality aftermarket magazines from either Chip McCormack, Tripp Research or Wilson Combat. Most factory magazines are junk even though 7-round mags generally have fewer issues then 8-round magazines.
Start here; if you still have issues then you will need to dig deeper, but these usually solve most issues.