Random websites wont load on x64 machine - why?

[peegee]

I have a newish x64 workstation, and a few random webistes simply wont load on it - like Craigslist. its very frustrating. 98% of sites are fine - its just random ones that give me "problem loading page" and "the connection was reset"

I have no child or website blocking software on there that I know of.
its connected to a cable modem router, and I have an old XPPro machine on that same router, and it can get through to those same sites no problem (so I guess its not the router).

Makes no difference if I use Firefox or IE. no result on either.
what's up? any suggestions, as its driving me nuts !

 

[peegee]

ps my hosts file is normal:

# Copyright (c) 1993-1999 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

127.0.0.1 localhost

---

oh and pinging doesnt work - for any site at all
which is weird - what am I doing wrong?

firewall?
router?