I actually tried sending PMs from a couple different computers and got the same thing. Anyway, I just did what you said with Chrome and clearing out everything, and now the PMs do work. Initially, the person's profile pops up, but then I can get a 2nd box that pops up for PMs. Also, for the 1st time I saw some old messages I had. These did not show before. They were just spam, anyway.
Any idea what causes this? As I said it happened to me on a couple different computers and seems to happen to some others as well. Is it a glitch of some sort you can get fixed?