Assuming you are quilting on a domestic machine rather than a long arm, there are 3 possibilities I'd suggest:
1) It's the thread. Thread is almost always the culprit for these kind of issues. If you can get a different brand/weight of thread in the same color, I'd try that before anything else ... especially since your machine was working properly before.
2) If you're Free Motion Quilting in the border, you need to change your machine settings & practice, practice, practice. Your stitch length should be set at "0". You need to either drop or cover your feed dogs. You need to switch to a Darning foot. Your needle should be size 80 or 90 (top stitch, quilting, microtex or universal needles could all work depending on what you're looking for). YES! I would definitely change out the needle. I've generally heard you can go 8 hours on a single needle. Sometimes I get a little longer, sometimes a bit shorter depending on the material & the stitch design.
3) If you have successfully stitched the pattern you're using in your border before & changing the thread doesn't help, my last suggestion would be to adjust the tension on the bobbin case. If you own one of those Towa tension gauges, this probably isn't a huge deal. For the rest of us, it usually causes as many problems as it solves. If you have an extra bobbin case lying around, do your adjustments on that. If not, I'd suggest getting a Sharpie (permanent) marker & marking a tiny line showing where your screw is now. Then, turn it to the right 1/4 turn & check to see if you still have problems. If needed, continue adjusting in 1/4 turn increments until the loops are gone.
Good luck!