Question : Cant go online but can ping

I have a windows XP computer which connected to the domain. When i log as administrator I can go online, but when i log as the regular user ( who s been using this computer for a while) I cant go online but i can ping any web address. This happened today.
I also updated the computer to Service pack 3 and IE 8. Still i am having the same issue.
Why is it one user can go online and the other cant? How can i resolve this issue?
Please help me experts

Answer : Cant go online but can ping

1) try with another user - if still the same
2) try system restore to restore the system back to a day where it was working - if still the same
3) try repair install of XP over the existing installation (second "R" in the blue installation screens), normally you will not lose any data, programs, etc.

now i'm off to bed.
ciao ;)