MSI UI question

Hi all,
We are using v4.5 version of windows installer.
We have the following bug:
we have button that is a bitmap control style type, meaning it points to a
button with bitmap on it (the same control).
We have background to this dialog which is also a bitmap.

The problem is that when launching the msi, the dialog button dissapears
until we go over with the cursor.
How can we solve this problem?
Which MSI DB change (attribute change or other) should we do in order to
make this button appears normally with the bitmap?

BTW, we have tried setting tab stop to false as we found in one of the
articles, but it creates other tab problems.

Any help will be appreciated,

Thanks in advance,
Limor & Eran