SOLVED by updating to the latest Latest DxTory 2.0.128 instead the Stable Release
old post:
after fixing my last problem (http://forum.exkode.com/index.php?topic=851.new;topicseen#new) PS2 worked fine, until i played a few hours and suddenly the game slowed down to 20fps and crashed.
My system drive was full caused by C:\Program Files (x86)\Steam\GameOverlayRenderer.log (http://pastebin.com/uEAqzLxx)
(had to cut the file because it's grown over 100MB in the seconds i can turn of Dxtory)
The file is growing in the loading screen with up to 20 MB/s until my drive runs out of space.
This only happens with Dxtory activated, after closing Dxtory the game works fine (instead of crashing like before).
I already deactivated the steam overlay in all of my games, so no this isn't caused by Steams overlay feature.