Tooltip and Errorprovider problem

[Issac]

Hi,

I am writing a program which will be used in Win2000 and
Win98 platform. The program include a Form (called
myForm) which has a TextBox, Tooltip, Errorprovider and a
Button.

Tooltip will be set with TextBox content and Errorprovider
will be set in TextBox Validating event if it is empty.
The Button is actually pop (ShowDialog) itself (myForm).

In Win2000, everything is fine,
but in Win98 or WinMe, there's a problem.

Problem:
I run the program, 1st form appear, I type something on
TextBox (tigger set Tooltip), then click Button to pop a
2nd form and set its Textbox to empty (trigger
Errorprovider check). The 2nd form will lose focus and
1st form will bring to front. As long as I click on the
1st form, the 2nd form will appear up front again.

This problem only happen in Win98/WinMe but not in Win2000.
Can someone give me a hand on this please?

Thanks.