PowerBuilder 10.5 issues with Yield function

Hi,

I am not a PB developer, but unfortunately, assisgned a task to troubleshoot a PB (10.5) issue, as follows:

We have a Yield() call in a loop lasting one hour:

    DO
        Yield()
    LOOP WHILE NOT gb_Continue

When our application gets into this loop, it uses 25%, 50% or even 100% CPU, apparently depending on the numbers of CPU cores. And furthermore, when we close the application, the process stays in the task manager. The platforms are Windows XP and 7.

Any idea or solution is highly appreciated. Thanks,

Allan Zh