It is because of random things like this that sometimes, just sometimes, I hate Windows.
I am having the same problem with both the All CPU gadget and the Network Meter: a small white box displaying nothing but < inside it; hovering over them reveals only the close and drag options.
I know that the RC build of IE9 made my gadgets constantly increase the usage of RAM during a period of time, but they worked perfectly normal. And even after a fresh (clean) install of Windows 7 and the official beta of IE9, they were still working properly.... until just now.
Last modification I did was uninstalling Shark007 codecs, and adding ChromePlus to use alongside IE9b. I haven't made a restart after installing this (there was no need, I thought). And just now after turning on the PC, these two gadgets were bugged. An Adobe update for PS CS5 came up and I skipped it, but the gadgets were already not working. An ordinary restart didn't work and, since the only way to get the Weather gadget working is to patch a .dll file in the Sidebar folder, I thought that perhaps if I restored it to the original Windows 7 .dll these gadgets would work, but they don't. So I'm out of any ideas...
I am not a fan of System Restore, but I do have Revo's uninstall point for when I removed the codecs. But I am really not content with using it.
Oh, yeah, another thing. Reinstalling the gadgets is useless, too, I remember that from the last install of Windows 7, before I did a clean install (Dec 29th). Restoring the gadgets (via Start menu search) doesn't help either.