I've checked for other with the same problem and found only three suggestions (reinstall, remove an update and restore files associations).
I haven't installed any updates, i've tried to reinstall the whole shabang (successfully) and i tested to restore the file ass'es. All to no avail.
When i click on the CSS-files i still get the message:
"The operation could not be completed. Undefined error.
That goes for all the projects and only CSS files (as far as i can see). The sites work properly as before. It's just the IDE that can't open the darned files! Suggestions?
