Oddly enough, these do not work on the American version of the Optimus 2x (T-Mobile G2x) running the latest 2.3.4 update. They don't even show up on the widget list once I install them. I tried restarting the launcher (I've tried ADW EX and the modified Optimus 2x launcher available on these forums) and rebooting the phone. They show in my apps list when I view Manage Applications in the system settings, so they're definitely installed, but just not working.
edit: must be LG's OS that blocks them, because CM 7.2 nightly for the G2x works.
If your Memos widget is crashing, get the LG Memos app from here. That fixed it for me: http://forum.xda-developers.com/showthread.php?t=932536