No video with Plex

I have an early 2010 Mac Mini that I use as an HTPC. I mainly use it with Plex to watch channels like Hulu, PBS, CNN etc. A few days ago I noticed that Plex stopped displaying video content for some of the applications. When streaming starts, you can hear the audio but the display stays with the previous menu.

I recently downloaded the new version of Adobe Flash. Also, like a day or two before the problem happened, I saw an alert message about a problem about Phyton while I was watching a show. Back then I didn't pay much attention to it, but apparently it might be related to the problem.

I cleaned and reloaded both Flash and Plex, as an attempt to fix it. I also downloaded Silverlight but nothing helped. I noticed that when I put Plex back in the computer it came back with all my files, applications and preferences. So maybe it was only a problem with preferences.

While all these are happening with Plex' Boxee, XBMC and Hulu Desktop work as before, without any problem.

Did anybody else have a similar problem with Plex or do you have any suggestions?

Thanks