yuna49 writes "Various people are reporting that the MS07-040 patch for .NET released on Tuesday can cause a variety of seemingly unrelated problems. According to the SANS Internet Storm Center 'the reports we got so far seem not to lead to any specific thing that happens in many cases, just various things going haywire.' Some commentators on The Register's report of this story indicate that the patch failed to install at all, while others report things like the mouse suddenly failing to work or long periods of hard drive thrashing. In some cases a hard reboot seems to fix the problem, but other reports suggest that a reinstallation of the .NET framework itself is required. The problems may be related to the MSCORSVW.EXE process which recompiles all the .NET assemblies when the patch is downloaded. While the recompilations are supposed to run as a background task, in some instances the recompilation will drive the processor to 100% usage."