Unable to access secure sites from Windows 7 with IE8

I have Win7 32bit IE8 and Firefox. This problem starts from few days. I am unable to browse secure sites ONLY if I am connected through corporate proxy address. If I connect from my home, no problem. With proxy enabled I can acces local intranet secure sites. Problem is only with internet sites. Tried the suggestions provided in the articles but no luck http://support.microsoft.com/kb/968089/en-us .
Tried with a different user id..no luck.
Tried with alternate proxy server...no luck.
Restore to a previous point...no luck.
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Is it the same on IE and firefox?
jzaveriAuthor Commented:
Its the same behaviour with IE and firefox.

I have already tried 813444. Few of the dll are not registering like initpki.dll, gpkcsp.dll, sccbase.dll,  slbcsp.dll  with error 'the specified moduled could not be found'.  I guess they doesn't get register on Win 7.
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Iain MacMillanIT Regional Manager - UKCommented:
sounds like something on your system or network (proxy or firewall) is blocking port 443 for external internet routed traffic.  Is it just the one system with this issue, are others on the LAN working ok (and you can get secure access from logging into another system)?

is the group policies up to date on the system?  if both browsers have the issue, i'd say its system wide and not restricted to IE8
Iain MacMillanIT Regional Manager - UKCommented:
could also be related to an IP or DNS issue on the LAN, can you check the NIC and check the IPv4 properties (IPv6 is normally un-ticked unless you have such a network) and try and set a manual IP and DNS settings of your DC's - see if that lets you get to secure sites.

can't be a system issue, if you can do it at home ok, must be policy or network related.  is there any AV/firewall on the system, other than the Windows firewall?

are the sites in your trusted sites list??  do you have Integrated Windows Authentication enabled on IE8 (advanced tab, towards the bottom of the window)?
jzaveriAuthor Commented:
Last night when accessing from home secure sites are opening. Connected through VPN to corporate network and trying opening with proxy enabled....no luck.
No other Win 7 machines are having problem. Its only this particular computer. Tried by disabled every possible add-on.
jzaveriAuthor Commented:
Found it at last. Its the Checkpoint VPN software.

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Iain MacMillanIT Regional Manager - UKCommented:
but if you are inside the network/LAN and being blocked you wouldn't running the VPN software???
jzaveriAuthor Commented:
yes, but this particular software has given us hard time in other issues as well.. like we cannot connect to another computer in the LAN unless we disable this software. But never the less as you have guided me almost to the right direction, I am glad to accept your suggestion.
jzaveriAuthor Commented:
Firefox and IE both are working now.
jzaveriAuthor Commented:
Thanks a lot to everyone.
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