Something makes Housecall crash/disappear

Anybody know what might be causing (Trend Micro) Housecall to crash and/or disappear? I suspect some malware/virus is in my computer, possibly also causing AdAware and SpyBot to declare "nothing new to download"... so I've been trying to do an online scan. I get as far as starting the scan - then the window just closes - *poof!* gone.

If anyone knows what's causing this, I'd be grateful - Adaware and Spybot don't detect it and neither does AVG. I can try using Hijackthis to get rid of it, but need to know what I'm looking for.

Thanks.
CG

 

oh, sorry. i should have said. I have Windows XP.
I'm sure some nasty thing is disabling my various security programs, including Housecall. I have used Housecall before - the permanent parts it leaves on the comp were left there, but lately when I try to use it, it begins to scan and then just up and closes the window.
I tried un-installing Housecall and starting over, but no luck. :cry

I will look into the suggestion from Halo and report back. Thank you.