Hello.
I did some testing, and the different progress bars do seem to be independent for me. I first created "IndependentProgressBars.vi" to test that they were at least independent in the same VI, and they are. Then I used this VI in a subVI called "TopLevelWithIndepProgressBars.vi", with the subVI setup to open its front panel when called. All three progress bars seemed to behave independently. I am using LabVIEW 7.1 (though I saved the VIs in version 7.0 just in case), and used the activeX object "Microsoft Progress Bar Control 6.0 (SP4)".
If you still have trouble, you might want to use the slide control I put in the subVI...