Error message "Attempted to read or write protected memory"

Hi,

I recently changed computer and although I can use Trados, I am unable to add or create a TM to a project that has already been created.

I am running Windows 10 Home Version 10.0.16299 Build 1629 and  SDL Trados Studio 2015 Freelance SR3 - 12.3.5281.10.

I have uninstalled and reinstalled, nothing changes.

When I try to add an existing file-based TM, I get the following error message:

Attempted to read or write protected memory. this is often an indication that other memory is corrupt.

External memory has thrown an exception.

If I try to create a new TM, I get the second message when I browse for a location in which to save the TM. Then, I get the first message and Trados shuts down.

I have Norton Security 22.16.0.247 as an anti virus whereas I had Kaspersky on the previous computer.

Any suggestions gratefully accepted!

Thanks for your time and help.

Mary