When accounting is using SO-F to print all unposted invoices for the day, after the last field (print linked documents) is completed and you tab off that field, a window pops up.  It's titled "Information" and it has the info icon with the word Customer " and an OK button.  Clicking on the OK button brings up the same window quite a few more times before you are able to continue to the rest of the task.  The amount of times the window pops up varies.  But once past that, things go OK and the invoices do print.  
 
What's the problem that's causing this popup window?
 
Thanks,
 
Val

Go into SO-A and on the opening list of SO, scroll all the way to the top.  I bet you have a blank record there that needs to be deleted.