Do you have the MainConcept plugin? I was having the same problem with XDCAM files. Anything bigger than 3.5 gigs or 13:40 min would not import fully into Premiere. I am running Windows 7 and Premiere CS4. I found that there was a conflict with my MainConcept Plugin. Premiere connected the XDCAM files fine before I installed this and after I uninstalled it.
I sent MainConcept a message regarding this problem and hope to have it fixed soon. I’ll try to keep you updated.