A number of things can cause this error, but it usually relates to your TOM_DATA folder. The easiest way to fix this is by renaming your TOM_DATA folder to something else (like “old TOM_DATA”). TOM should now open, but it’ll act like it’s a new installation; you can copy over the “data” folder from the old TOM_DATA folder into the new one to restore your information.

If this doesn’t work, try changing the ownership of the TOM_DATA folder. Right-click the TOM_DATA folder, click Properties, then Security up top, then the Advanced button near the bottom. On this screen, check to see if your user account is listed as the Owner at the top. If not, click Change, enter your user account, and then click Check Names. If your name becomes underlined, click OK. Then, check the box at the bottom for “Replace all child object permission entries” and click OK. Now, TOM should open!

If neither of these fixes your issue, please send in a support ticket.