An error 105 (actually any error over 100) can be translated into a corrupt file. It typically happens under one of two scenarios: abrupt power intruption (or users routinely doing a ctl-alt-del or power-off), or network/hardware issues.
The key to correcting this is to identify the program name (SOWMBA), the error no. (105) and the line no. (not specified).
Once you have those in hand, you'll need to contact the people that sold you MAS90 (or Best). They'll take that information and lookup exactly which file is corrupt. They can then walk you through repairing it (which is very quick and simple). A responsible MD/Best support person would also inquire into the reasons on why this happened (power outage, network setup, etc), so that this situation can be prevented in the future.
It is EXREMELY LIKELY that all of your data is okay. I can tell you from experience that the SOWMBA program is the program responsible for S/O invoice batch selection -- so the file most likely corrupt is either SOO (the batch file that simply contains a record for each batch & the date & user that setup the batch), SO5 (your invoice data entry header file--contains invoice header-level info for all invoices in your system, regardless of invoice batch), or SO5XXXXX (the invoice data entry file containing the header-info for just the invoices in that batch).
MAS90/200 comes with a utility to repair these files -- and like I've said, it's quite good. The >100 errors typically indicate a "bad index" or "key".. so the actual data is in good shape -- the system just doesn't have a good way of accessing it. The repair utility guts the data out and rebuilds it into a new file, thereby repairing the index/key-table.
Best of luck! Let us know how it all turns out!