Can't open any more databases error

[Di]

I've converted an Access '97 database to Access 2000 and
now I'm having problems that I didn't have before. When I
try to access records on a form, I get error messages that
say "Access can't open any more databases" and "object
invalid or no longer set", and that the "expression is
typed incorrectly, or it is too complex to be evaluated".
I didn't get these messages with the Access '97 version.
Can anyone help me fix this?

Thanks,
Di