non-hinge pin door noise roller help!

My drivers side door makes an awful cracking popping sound when opening and closing. I can hear that the guide plate / roller is where the noise is coming from. I can also see that the roller is not rolling freely and the guide bar has made a couple wear marks at the point where the roller doesn't want to roll any further. FYI.. The pins and bushings are fine.. and thats not the issue. Has anyone had this problem? solution?

oh yeah and also I have a 98 2wd 4 door blazer with 117,000 miles.
thanks