Sablotron ISAPI and IIS

[Anon]

I have the following system. (the latest versions of all)

Win2k
IIS 4
PHP 4.5
Sablotron
Expate

Everything works fine if I run php as a CGI app. If I install it as an ISAPI filter, PHP works fine, but as soon as I run a Sablotron function it brings my server down, giving me a 404.3 (too busy).

Any ideas? I'd prefer to run ISAPI but it's not that big of a deal.

Thanks.