Open Dashboard and see, what widgets might cause them, or even remove them one by one to pick the faulty one.
Or use the FORCE QUIT command in Activity Monitor to restart Dashborad and see if it returns.
What do you need the clock widget for?
Anyway, you can remove one widget, then check Activity Monitor to see, if it is the culprit. If it is not, remove the other and repeat.
And if they aren't the culprits, you can add them back.