VBA and SQL -

I have a VBA application interacting with SQL tables.
I am trying to do a simple lookup:

strNumLookup = DLookup("[tblPosting_RefNumber]", strTable, "[tblPosting_RefNumber] = '" & strNewNo & "'")

and it keeps screaming with this error:

ODBC – call failed. (Error 3146)

Any Suggestions???????? I can't see any problem with the way I am doing the lookup, so maybe a fresh set of eyes might help.

Thanks