CAUTION: This solution needs advanced Operating System knowledge. Consult your system administrator for help. Sage isn't liable for issues caused by improper changes to the Windows Registry. Always back up your data before applying advanced solutions.

 NOTE: The problem could be caused by pending Windows updates. First try restarting the computer. 

Workaround

1. If in a network environment, attempt to sign into Remote Data Access from another PC, as Windows updates are machine-specific. Normally, this allows for a successful login.
2. If the same error occurs, proceed with the steps below.

Rename Userpref.DAT

1. Find your company's data location. Refer to How to locate company directories.
2. Close Sage 50.
3. Open File Explorer and browse to your company directory.
4. Locate the Userpref.DAT file. Right-click it and rename it to Userpref.OLD or something similar.
5. Open Sage 50 and verify that the issue no longer occurs.

Damaged Windows user profile

• Create a new Window user profile. See Microsoft knowledgebase Article 81151. Contact your IT or system administrator for assistance, if needed

https://support.microsoft.com/en-us/kb/3175443