It happens to all of us at sometime, all of a sudden a file you need isn't there or if it is, it is corrupt.
This happened to us yesterday, a few minutes left of the day time to just apply some payments to our accounts package!
Disaster strikes, the package refused to open. After a little bit of playing with repairing the software, a uninstall followed by a reinstall and patching of the software was needed. Once this was done the software was at least working, however it couldn't open the company data file.
After downloading the data file check tool and then running it, it was evident that the data file had also been corrupted. not to worry this is where having a valid and off-site backup worked wonders, I first tried the latest back up which had been done around the time of the issue, however this was corrupt, and so I retrieved the file from yesterday morning, and then all was right with the world. (Well after about 15 minutes of redoing the transactions from earlier in the day)
Although it took time to get through each stage, it was worth it. We have been called in try and retrieve and repair files like this as no back-up has been done for a while.
Having it stored off site is the last piece of the jigsaw, not needed in this case, but if something had happened to the office, I could have relatively easily rebuilt everything.