How to fix Link2SD's "read only file system" error

A few months ago I had trouble with my Android phone with Link2SD installed (in "root mode"  of course). Whenever I wanted to update an app on the partition the error message appeared "read only file system".

Furtunately I found the following entry in the xda developers forum: http://forum.xda-developers.com/showthread.php?t=1493649

The explanation for the error message from Link2SD is an error in the EXT2/3 file system that causes that no more files can be written on the partition unless the errors are fixed. The solution described in the forum worked like a charm for me:

1. Boot GParted as a Live-CD (in my case in Virtualbox)
2. Insert the SD card (and connect it to the Virtualbox)
3. use the action "Check" within GParted to check the partition on the SD Card - this will also fix the file system errors

Thanks to everybody in the forum who wrote the solution and saved my day.