You probably have a problem with tender types. Have you been running any SQL Statements?
There may be a Knowledge Base article on Customer Source regarding this, but you should probably either seek help from your reseller or open a support incident with MS. This is pretty deep into the RMS weeds.
Is this happening on all registers, or maybe only on one register that isn't used as often?
If there is a register that you can still open Manager on, you could try this: go to SO Manager and create a new register (Database/Registers/Register List) go to the problem PC, Open SO Administrator and go to File/Configuration - on the Register Tab, change the register number to the newly created register. You should now be able to open POS and Manager - however, that broken batch would still be sitting out there, so you should try to get it resolved anyway.