Slow Eircom Broadband

hi all

Basically we have 4 pc's here in work and there all on a network using a ( D Link 10/100 fast ethernet switch ) for the network and standard netopia modem connected to it

anyway when im downloading from ituns or music or video the upload speed is 280/per second and im sure thats a good speed for 3mb broadband

but when i go to browse internet it takes forever to upload pages or sometimes takes too long it says cannot connect etc etc
try again and it connects

i have norton 2008 on the system up to date and regulary scanned , i know that doesnt mean **** but its something , i also have spybot updated and scanned , and since read through the " think i have a virus page " od these stickies and installed various adware removers etc and still no use

now 1 pc had limewire which i got rid off asap as i know you can get everything from them

any help much appreciated