This is relatively recent, it's only been noticed since about July. It's been identified as malware, but you will probably need one of the heavy-duty removal tools to get rid of it - getsusp or ComboFix. Both of these are tricky to use and I strongly advise you to run them under the guidance of one of the forum experts.
There is a getsusp group here on the forums at https://community.mcafee.com/groups/getsusp30-beta-feedback
Note that this is a Beta product, and you need to join the group and ask for assistance.
Over on the Microsoft Answers forum someone with this problem was advised to download a tool from Trend Micro :
The answer was ticked, so maybe it helped. But be advised that this too is a Beta program (I checked the link to see where it went). That page also lets you run HijackThis, which will list all of the programs and processes which run at startup. You might find something in the output that tells you what it is that is generating this message.
The "bot not crypted" message has been mentioned in a number of forums but I haven't seen anywhere an explanation of its cause, nor any confirmation that suggested fixes have definitely worked. So let us know how you get on with identifying it and getting rid of it.
(Edit) Correction. Over at SpywareHammer one person's problems at least were fixed by running ComboFix.Message was edited by: Hayton on 11/11/10 02:01:32 GMT