Error wirth Runtime

Hi last week I downloaded Firefox 1.5..0.4 and for the first few days
it worked fine but now it opens my frontpage then a panel comes up
saying "This application has requested the Runtime to terminate in an
unusual way" When I click ok it closes Firfox.

I use Win98 se

Can anyone help ? I tried re-installing but that did not work.

Thanks

Pete

Pete