I think there is a bug in 6.2.3:
When I try to use the comment feature (CTRL + K) in commenting a particular line in my CSS its successful but when trying to uncomment the same line it crashes:
An exception occured. Notepad++ cannot recover and must shut down.
The exception details are as follows:
Type: Access Violation
Exception Address: 0x00401991
I don't know if this issues has already been addressed in the newer versions but apparently uncommenting a line in CSS files doesn't work in mine.