explorer comes up with cartoon and other images

In the past couple of week we intermittently get cartoon images or other pictures when trying to go to any legitimate website i.e www.google.com or bbc or others. this problem then goes away and then appears on another PC in the network, I scanned the PCs for the virus and it is clean. I called the ISP however and they had to restart their Cache server last week and give me the assurance that it should now be ok. But of course it keeps happening - not on the whole network but a machine here and there and the same machine will be fine after few hours. Let me know of your thoughts on this or if you come across the problem what you did to resolve.

Thanks

We a similar issue a little while back. I rebuilt the squid proxy box and all seems fine now (We have our squid proxy box on site though!).

Did it still load these images straight after they cleared the cache? The problem with ours was even after 'clearing' the cache, the cache remained there.

We do not have a Cache server, so it is something to do on the ISP side - they said they rebooted the Cache server last week but the problem is til there I emailed them the snapshots today and see what they come up with.