Without seeing a log file I can't be sure of the cause, but if you're trying to save the backup to a network location please try saving it locally instead.
If you still get the error please open a
Support Ticket and
report your problem so that we can check your log file and see what is going on.
It is possible to remove old hands from your database, although it is simpler and faster to
filter instead.
If you do want to remove the old hands, you could either:
1)
export what you want to keep and import those to a new database (so that you keep your full data in your old database) - see Database > Database Management for creating a new database.
2)
Purge your old hands. This is permanent though, so make sure that you have your hand histories before you do it in case you ever want to use your data again, and can also take quite a long time if you have a large database.
(For a large amount of hands it will likely be faster to export/import to a new database than to purge.)