During the last days, my Windows XP Prof installation shows slowed down keystroke responses in certain applications (e.g. firefox, thunderbird, RDP sessions). Also, window update rates seem to slow down, e.g. the cursor blinks much slower in this firefox text edit field into which I type this very text. While this unresponsiveness makes typing quite annoying, it does not exceed 500-1000ms. In some respect it resembles using a Remote Desktop session over a very slow connection.
That being said, processor load as reported eg. by Task Manager is quite low (0-10%) on my 2.6Ghz PC, little to no harddisk activity, in other words it's not the computer experiencing constant overload. It's just slowed-down typing or window-updating, respectively. Application startup times and stuff like that is normal.
I am wondering about the reason for this, more specifically whether this might be due to some keylogger/backdoor activity in the background? But I couldn't track down anything suspicious. Strange that it only applies to certain apps, while e.g. typing text in notepad is fast as normal.
Any hints? I would really appreciate any help that makes typing and my nightly sleep (backdoor?) comfortable again...