Cisco Systems VPN Client(Cisco EasyVPN) Not Being Connected

[bellskar]

Hello All.

I am very new to this forum after searching a google alot and this forum as well. I didn't make it to find the solution already discussed as mine. so posting this new headache (for me atleast) to ask for the solution for it.
so here it is.
I was using Cisco easy vpn v4.x previously to connect to my head office. that was very fine with it. but for some reason I had got trouble with my Windows XP that finally leaded me to have a fresh XP installation. so I did it. and now I have fresh Windows XP Pro SP3 on my laptop fully updated from microsoft website. (previous installation was also with SP3 fully updated)
and now the problem what I have is. My Cisco Easy Vpn client is not connecting to the PIX at my head office.
I have the same settings that were in my previous installation.
I also noticed that it discovers the Host successfully as if I put a wrong IP/Host it tells me with an error after a timeout occurs. But If I give the correct Host to the PIX at my office. and click the Connect button then it just takes a second or two by changing the status from
[Contacting the security gateway at xxx.xxx.xxx.xxx]
to
[Not Connected]
and that's all. no other authentication error. nothing else.

I have also tried with newer version of VPN Client that is Cisco Systems VPN Client v5 but the same problem persists.

I'll really appreciate any solution from all of you.

hoping for quick fix
thank you
regards
Khurram.