Problems with various websites unless accessed through proxy

[#1]

Having a strange problem with my internet. On all the systems on my network, including my iPod Touch, certain websites won't load at all (usually forums) while others take a very long time and on others images don't load. However, when I visit these websites through a proxy they work fine and load immediately with no trouble at all. These are my attempted solutions:

• Changing the default DNS to OpenDNS.
  
• Disabling the firewall.
  
• Using CCleaner to clean all the browsers.
  
• Scanning for malware.
  

I've had this problem for about a week now, are there any other solutions I could try?
Thanks.

[#2]

might help if you gave us an idea what sites these are

[#3]

answers.yahoo.com
webhostingtalk.com
overclockers.com
guardian.co.uk
They are just a few sites I noticed today, I find a new ones that won't load daily.

[#4]

See if you can tell the name of the servers it gets stuck on, almost certainly the images of some of those sites come from different servers, and it will be that javascript on various sites will also come from different servers.
I suspect you have either a routing problem or some of the content you want is on a CDN (content delivery network) or some other server that Plusnet views as needing to be throttled.

[#5]

hmm they all seem ok here

[#6]

Turns out is was my host file, I cleaned it and replaced it with the one generated by Spybot and all was fine.
Thanks to both of you for taking your time and attempting to help though.

[#7]

glad you got it sorted