First of all, ensure that this option is enabled in your profile. For that, click on the Profile link in your top navigation bar and go ahead to the "Preferences" section. Tick "Yes" for the entry "Pop up window on new Private message".

If it's already done, then your problem is caused by a popup blocker. Some navigators are equipped with a popup blocker. Below are some instructions on how to disable the popup blocker in your browser (IE and FF). If you another browser, check the helpfile or search within the options or settings.

Firefox:

In your main menu, on top of the address bar, find the menu entry "Tools" and select "Options". Click on the "Content" tab. You will see the exceptions button now nearby the label "block pop-up windows". Click it and enter your forum URL as allowed site. If you have a customized domain name, you should add both the custom domain and your original forum address.

Internet Explorer, on Windows XP Service Pack 2/3:

Click on Tools (besides Favorites) then on Internet Options



Click on the Privacy tab



In the Pop-up blocker section, go to Settings



Type the forum address (you can omit the http://...), then click on Add



Google Chrome (solution thanks to Loki)

Options > Under the Bonnet > Content Settings > Pop-ups > Allow all sites to show pop-ups

If you have the MSN toolbar

While you are on the forum page, click on the little arrow just beside the Blocked pop up, on the toolbar, then click on Allow this site to open pop up windows. The pop up windows of the forum will be then allowed.

Tutorial from: http://help.forumotion.com/frequently-asked-questions-f5/i-recieved-a-pm-but-no-pop-up-opens-t8331.htm

ah, it was because of pop-up blocker?

thanks a lot!

O so thats why i always have to remember to look at the meesage nar to see if i have a new PM thanks this is useful

I think my CPU is slow... It doesnt even say I have a new PM until like 15 mins later.