This problem hasn't been reported in so long that I've forgotten how to deal with it. (Considering the dearth of system related issues in recent years, it's almost like an old friend. )

All of a sudden, I'm getting error messages when I try to move items to the trash.

Restarting fixes things...until next time.

HELP!

Thanks.

This StackExchange thread proposes a fix.

Thanks for the link; that thread may have pointed me in the right direction.

Relaunching Finder repeatedly isn't an option, nor am I about to get involved with chmod without knowing precisely what I'm doing, but the talk about permissions inspired me to repair home folder permissions, and it seems to have turned the trick.

I haven't had a recurrence of the problem in a while, even after restarting.