I’ve finally solved the problem of:
http://mail.google.com
“Grr! A popup blocker may be preventing Gmail from opening the page. If you have a popup blocker, try disabling it to open the window.”
The problem for me was Norton Internet Security / Symantec Client Firewall. Although you might not think it, this program includes an ad blocker and popup blocker, and doesn’t warn you when it blocks ads. (Same with network connections it blocks.)
Even when you right-click its icon and choose Disable, it might still block popups. Open the System Status window, click Ad Blocking, and then choose Turn Off. You’ll need to refresh the page for changes to take effect. You might be able to further configure Ad Blocking to your tastes by choosing Configure.

Thanks a lot! Adding mail.google.com to the symantec ad blocking allow list did the trick.
Thanks for the info. It worked. I have Norton 360 running Vista. I didn’t have the problem until I downloaded and installed the free add-on anti-spam pack. The ad blocking option was already off but the popup blocker option was on. Once I turned off the popup blocker everything was ok.
Dear,
My problem is that whenever I open my add contacts Address bar after clicking that optin this messages “Grr! A popup blocker may be preventing Gmail from opening the page. If you have a popup blocker, try disabling it to open the window.†appears on my screen thatswhy I am sufring form this problem for few month.
kindly reply at an earliest.
Thank’s
UPENDRA PRAJAPATI
Actually, for me, it was Google toolbar’s pop up blocker. When I make it from “Blocked” to “Pop Ups Okay”, I still can’t get the pop ups. But if I hit the “control” key and then the link I want opened, it lets things open up. My Norton turned on or off doesn’t seem to affect anything.
Awesome!! I googled the problem and go your web page… and VIOLA!!! Unfortunately, i still can’t get hotmail forwarded to gmail…something about hotmail not being using POP?
I hoped to avoid having everyone change their email address books, but it looks like i’m going to have to anyway. Thanks for the tip though, it worked!!!!!