[OSM-newbies] problem with loading openstreetmap on one computer but not the other

[JW]

1) i think OSM is great, have added small features to my local map and just
donated to the server appeal
2) on my work laptop with my home internet connection OSM loads fast and
displays fast
3) on my personal laptop (better spec than work one) i get the same result in
ubuntu/firefox winxp/firefox winxp/chrome which is that i get lots of status
symbols like

'connecting to paypal.com'
'connecting to a.tile.openstreetmap.com'
'connecting to b.tile.openstreetmap.com'
'connecting to paypal.com'
'connecting to c.tile.openstreetmap.com'
then a few MORE OSM coming soon tiles might appear (i have not touched zoom)
then some tiles might come up with others blank or MORE OSM tiles
then status changes to done presumably on some time out

sometimes some map does appear but i try to zoom then it is horrendously slow
and i get a repeat of the above.

performance does seem to vary and is sometimes worse than others...

things i have tried
-------------------

1) getting rid of local internet files and cache - didnt work

Help!  This is making OSM and POTLATCH unusable on my home computer.

JW