Originally Posted by kovidgoyal
There have been no changes to the server in 0.8.30, but feel free to downgrade calibre, old releases are available from: http://sourceforge.net/projects/calibre/files/
Though if your PC is freezing, the problem is with your PC, most likely an antivirus program.
Thank you for the quick answer, AVIRA is running on my system since years, but i switched of AVIRA for a unsuccessful test.
If there was no change to the server, was there any change to T1 Plugin?
Could you please be so kind and have a look to the txt file, with the error.log?