Have you found a solution yet?  I have the exact same message and haven't been able to open the program since.  I tried contacting support on Friday but the wait time was excessive.  Will try again tomorrow (Monday).  

No solution Dannn.   I did get thru to tech support but their only suggestions were 1) reinstalling the update or 2) they sent me a link for the 2013 version but that was the release 3 version.   Uninstall the current (upgraded version) and then reinstall the new  Thinking that the full program install might work better than just the update.   Neither one worked.    

I uninstalled again, found my original 2013 download and then reinstalled the Jan/13 PR update and at least got back to where I started.     I've advised my co-workers with copies of the program NOT to run the upgrade, which will work for awhile until we start getting company files in that have been upgraded

Not very happy at the moment

Go into document folder and check to see if you have folder called Sage Software, then Simply Accounting, then Download, in there you should have a file called SA_20133CPUP1, if so then try doubleclicking on that to get the download going again. I have had one client with same error as yours and was able to successfully download update using this method and opening up Simply again.

Hi

If you get this error, mostly likely the reason is related to .net 4.0 corruption.  Since you are using XP, there is no .net 4.5 you can download and install.  Suggestion is to first repairing your .net 4.0 and then reboot.  You can find the .net repair tool from Microsoft Download Centre (www.microsoft.com/.../details.aspx).   If repairing .net 4.0 does not fix your issue, you will have to uninstall your sage 50, uninstall .net 4.0, reboot and then reinstall the software.  

The link below is a Knowledge Base article regarding this issue.  You can have a look at it.

Error: “Sage 50 Accounting has encountered an unexpected error and needs to close”

Hope this helps

Hi

If you get this error, mostly likely the reason is related to .net 4.0 corruption.  Since you are using XP, there is no .net 4.5 you can download and install.  Suggestion is to first repairing your .net 4.0 and then reboot.  You can find the .net repair tool from Microsoft Download Centre (www.microsoft.com/.../details.aspx).   If repairing .net 4.0 does not fix your issue, you will have to uninstall your sage 50, uninstall .net 4.0, reboot and then reinstall the software.  

The link below is a Knowledge Base article regarding this issue.  You can have a look at it.

Error: “Sage 50 Accounting has encountered an unexpected error and needs to close”

Hope this helps