Can only upload one file with PHP; two results in 'Connection Interrupted'

[Rob]

I'm running PHP 5.2.3 via fastcgi with nginx. When I upload one file via a form,
it works perfectly. When I try to upload two files, however, I get the
'Connection Interrupted / The network link was interrupted while negotiating a
connection. Please try again.' error message. The file sizes aren't an issue as
I checked the max post size, etc in my PHP config. I'm thinking it might be a
nginx/FastCGI problem?

Anyone have any ideas what's wrong?