Hmmm, this is odd. What version of wyUpdate and the AutomaticUpdater are yo using?
Don't use the same AutomaticUpdater GUID as the wyUpdate GUID. They have to be separate things. Also, I'm a bit unclear how you're reproducing this.
What GUID are you using in the AutomaticUpdater? (Please copy & paste exactly what you're using). What GUID are you using for wyUpdate?
The error is confusing. I managed to seem to repair it however.
What I was doing was this:
I built WyUpdate for release pointing to a non-existent URL that will be populated once the actual released version is ready. As such, WyUpdate was failing (on purpose) trying to connect to the URL that didn't exist. I did this purposefully figuring that the LastCheckedDate would update and it wouldn't bother me.
I'm speculating, but what it looks like is when WyUpdate searches for an update at a location it won't update LastCheckedDate when it fails. Once I uploaded a fake update to the web server it found the update, said it was up to date, and never checked again. This is what lead me to my conclusion.
I don't think I read this anywhere in the documentation for AutomaticUpdater or WyUpdate. I could be wrong though. If it's not in there (and I'm correct here), I would definitely recommend putting it there.