error msg after reboot: uncaught excepton pushModal screen etc.

Don't know when/why this started but now each time I reboot my device I get an error message that says:

uncaught.exception:.pushModal.screen.called.by.a.n onevent.thread

what's this mean, and what might have caused it to occur/reoccur?

I've tried a number of fixes: removing a few apps etc., and next will be to wipe the device but still have to wonder what's happening.

Learned from other sources that the cause was likely a conflict between applications which would be corrected after a wipe of the device. I wiped mine, but did not restore the applications to avoid the possibility of restoring whatever problem was hidden within the apps. Rather I reinstalled each application separately and so far all is good.