That doesn't appear to be either a JET or a VBA error number, Marius.
Trappable JET errors are numbered from 2420 to 3808 (see the help file
'jeterr40.chm'). VBA uses numbers 3 to 746 (1 to 1000 are reserved, but not
all are used) and 31001 to 31037. The error number 7787 might be coming from
a data source (are you connecting to SQL Server or another database other
than JET?) or from a referenced component. Do you have any references
included other than the default Access, VBA and DAO or ADO references? Are
you using any ActiveX controls?