I'm having the same problem.
My system is Windows 7 Ultimate x64 SP1, all updates applied. IE9 installed.
Uninstalled IntelliPoint 8.2 but even after a reboot this did not solve the issue.
I think the problem began after I installed a new graphics card - nVidia Quadro 600 along with latest drivers.
Killing sidebar.exe (or just switching off gadgets by right-clicking on the desktop) does fix the issue though. Sometimes I can restart sidebar and the problem does not return for a while.
I have three sidebar gadgets - two weather (two different cities) and one currency. Both are provided by MS as part of Windows 7 - these are not third party.
I would think there's enough information now for MS to be able to reproduce this issue and develop a fix, surely?