I'm an IT tech - I have a couple of clients with A55's on Vista Business connected on ADSL to Bigpond (Australia). Both exhibit the same symptoms - different locations, different modems.
When they start up their PC's they can browse the Internet for about 10 minutes, then they get time outs to all sites. This happens whether they use ie7 or Firefox so it's not a browser issue. When the www fails, I can open a dos box and still ping outside IP's and get DNS resolution (nslookup) so the Internet is still available!
There ar no viruses, spyware or other background processes or tcp activity that would cause this (monitored both). All drivers for network chipset are up to date. Firewall is not blocking otherwise the first 10 min would not work.
I've tried disabling Vista's new autotuning, but that makes no difference (netsh interface tcp set global autotuning=diabled rss=disabled). I've replaced their ADSL modems - same problem. Their hardware is new and passes all diagnostics - it's not a hardware problem.
Has anyone had the same problem and if so did you find an answer short of formatting the hdd and installing XP?
The router MTU is 1400, which should be fine for ADSL. The other PC on the same router is XP Pro and has no problems so the issue is related to Vista rather than the router. I've even tried a brand new (different brand) router and the same thing happens. It also happens with Firefox so it's not an IE7 problem. I've disabled the CA ITM firewall and the same thing happens so if it's getting blocked for some reason it must be hidden in Vista somewhere...
Yep - been there, done that. It makes no difference. It appears to be something Vista is doing - it's like it's gone into security lock down on Internet access... I did read that some older routers are not compatible with Vista's more aggressive broadcast packet flooding and MS have a test that you run from the PC in question. I ran that and all is well according to the results, so it's not the router either - to prove the point I put a new (DLink) router in and set it up - same problem after 10 minutes of browsing...