I am not sure if this would help or not , but I did have problem with some simple code that I had included Do,Loop.
The code worked fine when it was compiled using PBP3.0 but it did not work if it was compiled by PBP2.50B , which I had on an older machine.
The problem was solved when I changed the Do,Loop section to GOTO , and then the result from both PBP3.0 and 2.50B worked flawlessly.