I would also like to report this problem. It happens sporadically -- sometimes everything works fine; other times it doesn't. Unfortunately, I seem to be having the problem more often than not lately. This is with both v1.94 and v1.95. I'm running XP SP3 with a GeForce 9800 GT video card. I have not updated drivers lately (within the past several months).
As you can see in the screenshot below, the pop-up text block is entirely black. (The mouse is hovering over one of the Crushing Impact IOs in Stone Mallet.) Also notice that the top row of buttons in the pane is not there. I can
get them to appear by click-dragging another window over the Mids' window and "scrubbing" the other window around, but that doesn't work on the pop-ups, since they aren't there without the mouseover. Additionally, the information window in the lower-left corner either doesn't update on mouseover or doesn't update completely, depending... which is not indicated clearly in the screenshot.
When everything is working properly, everything continues to work properly. Only once do I recall everything "fixing" itself when it opened in screwy mode; I had minimized it instead of closing it and came back hours later. I have (rarely) been able to close Mids' and re-open it to find it happy. I use Mids' both when playing CoH and when not. (Sometimes just playing in Mids' is enough fun by itself -- by the way, thanks for an awesome and fun app!)
I forgot to mention that when I change either powerset drop-down selection, it does not update the powers list(s). I can get it to update the powers by more "scrubbing" with another window.
It really seems to be a refresh/redraw issue.