Since this issue has not plagued everyone, there must be some idiosyncratic issue that affects only some users. It could be an interaction with some unknown 3rd party apps, or it could be a sequence of events (upgrade, clearing of cache/app data, deletion/reinstall of widget) that is not the same for everyone. Has anyone tried (1) removing the widget from the homescreen (2) clearing both cache and app data (3) rebooting, and (4) then reinstalling the widget on the home screen? I would even be tempted to try all these steps only after a fresh reboot, or rebooting after each step.
Don't forget to look at the settings. The update to 3.1 may have changed some default settings for you. (For me, the accessibility checkbox was selected for me, which disables caps lock and other features on the on-screen keyboard.) Did some folks' 3.1 update uncheck the background data and auto-sync checkboxes?
I had a related problem on my Droid 2 Calendar app. It just would not sync at all, or sporadically. Drove me nuts. I rebooted, deleted widget, cleared app data and cache, turned of syncing, and rebooted before re-installing the calendar app and re-enabling sync, and all is now well.
At least if someone tries this we can see if that is a permanent fix.I don't doubt this is happening to some folks, but I have never experienced it with my 3G Xoom since day 1 adoption. Usually clearing app data fixes application weirdness. The only other option is a factory reset and updating the OS back to 3.1 before adding any 3rd party apps. Don't wanna think about that.
Cheers.