We have an issue on an SBS2003 domain whereby web pages intermittently have loading issues. Sometimes we get a DNS error in the browser, sometimes the web page doesn't load fully in particular images are missing, other times pages load fine, albeit a little slow. This affects all PC's on the network on all browsers. There is no problem with accessing files/shares etc on the server.
Also, we are having seemingly intermittent issues with exchange not receiving external email, sending seems fine and receiving internal email too.
The issue has stemmed from what we thought was a problem with the ISP DSL connection, with the initial fault being dropping connections. They tried some sort of 'reset' on the line which didn't cure the issue but improved the drop-outs. I noticed on the router that the ethernet connection light kept going off so I replaced the dedicated network card, this seemed to help a little but the ISP sent a replacement router anyway and we copied the config from the old router to the new one (ports/rules etc) and now we have a stable connection but are left with the web page issues not loading properly/intermittently.
I've checked the event viewer on the server and there was a DNS issue a few weeks back, but I think this was before we started having troubles. I've also tried opening DMZ on the router which makes no difference. I've also stopped all local software a/v and firewalls too, again, no difference.
My next step is to plug directly in to the router and bypass the SBS/domain - But my gut feeling is that there is something DNS related on the server which is causing this anyway, the question is, what can this be?
I've reported back to the ISP and they have washed their hands of the problem as they can see a stable connection and data transfer. The issue doesn't affect other web services such as logmein/dropbox etc.
advices very welcome!