Progress Bar Not Behaving Correctly?

I am using VB 2010. I have a process that gets file names into an array and then processes each individual file. To know the progress of the process as a whole I added a progress bar. I init the Max property with the number of elements in the array, set Value to 0 to clear the progress bar and then I start processing each file. Processing takes a minimum of about 5 to 7 seconds, so I should be able to see the progress.

The problem is that the progress bar does not correctly visually represent the advance of the overall process. For testing reasons I am using 4 files. When the first file is done, the progress bar is empty. When the second file is done the progress bar is filled 25%. When 3 files are done it is filled 50%. When all files are done it fills to 75% then immediately jumps to 100% filled.

The kicker is that when I uncomment the messagebox statement shown in the code example it works just fine! I added the DoEvents() then the .Refresh call, but there was no change in behavior. I left the .Refresh commented since I believe that it is redundant with the DoEvents call. I think it might be a timing issue where the progressbar does not attempt to update until after the .Refresh/DoEvents() statement, by which time is now processing the next file.

Code follows:

'Get the file specs into array.
'Set up the progress bar.
progressBar.Maximum = strArrayOfFiles.Length()

[code]....

I built the project into an EXE and ran it under Win 7 and Win XP. It works right under XP, but continues to show the above described behavior when it runs under Win 7.