Exchange 5.5 SP4 and OWA

I recently installed SP6a on my NT Server and then installed SP4 on my exchange server. Now when I try to use OWA, the page is displayed blank, weather I do it over the internet or by using local host. I removed OWA and replied the SP4 and then reinstalled OWA, and that works for a couple of days, but then it dies again. Does anyone know how to resolve this issue?