I think you may have just lost the link to the exisiting data file rather than anything more serious. There is occasionally a problem with data disappearing out of one fields when you type something new into another one and we have a fix that sorts this out. You are welcome to email me at TWR to get this solution. email@example.com
In the meantime have you tried doing a search on your hard drive for all files ending in ".uds" If you do this, I am sure you will find your original data files. Often when this has happened it turns out that the data is still there and it is just a case of the program not remembering where the file is kept in your system.