A family of Microsoft relational database management systems designed for ease of use.
First, MAKE A COPY of your frontend - it may be corrupted or it may not, but my suggestions below could make matters worse!
Then, try opening the frontend, holding down the SHIFT key if necessary to bypass any startup code. Take a deep breath, select all the linked tables and press the DELETE key to delete the links. If Access asks you "Really!?" say yes. (I told you to make a backup... right?). Then compact and repair the database.
Then use External Data... Link and create new links to the tables in the backend. Compact and repair the database again.
If this doesn't clear it up, post back with more details (such as the SQL of the query that you changed).