According to my discussions with Mercury’s Technical Support, there are several limitations that LoadRunner has when executing QuickTest Pro scripts. Apparently, your QTP Scripts cannot:

• access external files.
• use external libraries.
• have reusable actions.
• use shared libraries.
• reference reusable actions in other scripts.

The general rule of thumb that the tech support agent suggested was to ensure that you have all referenced code inside the script directory. This is to ensure that LoadRunner passes everything required of the test to each Load Generating machine.