On occasion Sage 50 Accounting using Remote Data Access will through an error trying to open a company file.
If the error is code 43 (File system error number: 43 in file", you will need to rebase the company on a computer that sill has access to the company file.
Open Sage and the company in question.
Select Help, then Support Utilities, then "Rebase Remote Data Access Company"
Sage will run through some prcoesses:
Once completed, you should be able to access the company on the other computers.