> However we have a need for backwards compatibility, ie to move data back from our Vista (Firebird) version to our XP (Interbase version). So far all attempts to backup from Firebird and restore under Interbase (7.1) have failed. Has anybody achieved this?

Sure. If this move is one-time operation, you can use any "data pump"
utility such as FBCopy or IBDataPump. If the databases must stay sync-ed
all time, you can use replicators, such as one by IBPhoenix.

SY, SD.