Although the Win32:ctx sounds scary, it's most likely a false positive .
http://www.avast.com/eng/faq_panda.html
This a false positive detection caused by Panda's on-line scanner not encrypting its virus signature files. Active Scan is the folder created by Panda's on-line scanner you can delete the whole folder. Because of its location in the windows\system32\ folder system restore may save a copy of this, so you may need to disable system restore, reboot and then delete it.
Hope this helps
John A
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