[AccessD] Error 3001 - invalid argument - What the . . . . ?

Out of the blue, I'm getting the above error (minus the "What the . . .?") in a proc that has been running rock solid forever.  It's in a block of code where I'm using DAO to write a record to a table:

.AddNew
!field1 = SomeValue1
!field2 = SomeValue2
.Update

Code is puking on the .Update line.

I suspect some sort of corruption, but all my usual remedies (decompile/recompile, compact/repair) don't seem to be having any effect.  This is probably my weakest area of understanding with Access, etc., so I'm not even sure I'm using those approaches correctly.

Hoping somebody might be able to suggest a more reeliable way to the problem . . . .

Don McGillivray