My windows, rear ones especially, have been gradually getting harder to put back up as well. A buddy of mine at work had the same problem a few months back with his driver window, which eventually got stuck down. Right now his X is in getting the other 3 window regs replaced.
How can Nissan not turn this into a recall issue with so many having the same problem? This is clearly faulty/poor manufactuing on their part. Anyone who has not already done so, PLEASE use the above number to report your problem to Nissan.