My site was down for 20 hrs on Thu-Fri, and this what my host had to say:
due inpart to the W32/Sobig.F@MM worm that had hit the internet on aug 19, 2003, we have been experiencing network slowdowns. This has staggered email, web and the FTP services that we provide to you. Please be advised that we are fully aware of the situation at hand and are working as swiftly as possible to return service to normal. At this junction there is no Estimated Time of Repair as network administrators are diagnosing and working to correct the problem
We thank you for your patience and understanding in this matter while we work to restore your website and mail services to 100%. As always, if there are any further questions, please feel free to ask us
I agree with Imaster - you should consider changing hosting companies. My primary hosting is based in New York - and even with the electricity blackout and Sobig, they have experienced zero downtime and no significant slowdowns. Your current company either didn't bother to apply the right security patches (if the servers are Windows-based) or are running too close to maximum capacity to allow for an email flood which can be caused by a mass-mailing virus.