I have seen this a couple of times on two different routers. One is a 3745 and another a 1811 running 12.4(15)T4 and 12.4(6)T11, respectively.
When we have IOS firewall running (either IP inspect or ZFW), we will experience intermittent slow HTTP connections.
Symptoms include page timeouts, CSS not loading and just overall slow performance. Disabling the inspection cures the issues.
Has anyone ever seen this before? Any ideas? Thanks!