It sounds like either the file has problems or your Access installation has.
Things to try (Keep backups of everything before you make any changes) :
- Open the file on another machine.
- Re-install Office or Access.
- Compact & Repair the file.
If none of the above work then you can search the web for providers who can recover properly corrupted database. No-one here is allowed to post links to specific sites as the rules strongly prohibit such behaviour (I will happily ban the accounts of any that try).
If it comes to it then I can give you at least one recommendation if you send the request via PM. I've not used it myself but have heard tell from others that it works in many cases. I doubt you'll need that though. I expect most services offered will do a good job. I hope you won't even need to go that far.