Page Up/down keys don't allways work.

Hello,

Page Up/down keys don't allways work.

When a PDF is first loaded the Page Up/Down keys don't work.
If I click on the body of the pdf with the mouse, then Page Down will work once.

If I click on the scroll bar, then Page Up/Down will work, until I click some where on the pdf.

The form contians wpViewPDF and Action Tool Bar components.
D7 on Win2000.

What should I try?

Thanks