As mentioned above try graphite powder or silicon spray first, I had a similar issue with my em1.

Initially I thought that it'd be the regulator as well but I took a closer look and the window had popped out of it's track, the rubber tracks were getting caught on on the glass when it was moving up.
I popped the window back in it's place, tightened up a few bolts and liberally sprayed it with some silicone spray and it's been fine for about a year now.