Maybe a dumb question, but why a different company? Aren't you going to collect $$ for these invoices and post cash receipts? Or, is it truly a different legal entity?
As for opening procedure failed, USUALLY it is looking for files that don't exist. Did you set the company up in macola system manager? When you turn the modules on, you should see it initializing the files related to that module. Compare the AR/OE/IM/SY/TAX files in the live company to the new company to be sure they are all there. If they are, go into the main live company and open the screen where you get the opening procedure failed in the new company. Open the pervasive monitor and note the files you have open for that session in the working company. I'm guessing there may be BM, PP or SF files opened in addition to the ones you would expect. Go back to the new company, turn on those modules, initialize all files in those modules, then turn them back off again. If you have feature items or pp items in your item master, you need to leave these modules turned on. Are you copying files from your main company to this company? Be sure you get all system level files as well as those that are module specific.
You can also get the opening procedure failed when you are out of pervasive licenses. The message isn't helpful, but it can be a cause. Check your resource usage in pervasive to determine how many licenses are in use.