Windows suddenly doesn't allow new windows to open

Hello, I'm having a problem with my computer (a Dell P4 1.4Ghz, Windows XP). It used to happen once in a while, but is becoming more frequent. It suddenly and without warning will not allow certain new windows to open. Some examples are e-mail messages (which open in a new window), clickable internet pop-ups, picture files (in a folder on the Desktop), right clicking with the mouse in the internet browser and selecting "Open Link In New Window", etc. etc. When clicked, the hourglass pops up for a second, but the window will not open. Programs themselves do still seem to open. The only way I've found to fix it is to reboot. If anyone has any ideas about how to fix this, I'd really appreciate it, it's driving me crazy!

Thank you very much.

Thank you for the response. I'm not using Mozilla Firefox...that's a brower, right? I'm using Netscape. And the problem doesn't just happen on the Internet, it's certain files as well that won't open.

It's not just in Netscape. The problem does only happen with certain files, as well as opening new Internet windows, but it's not a mouse problem. When the problem starts, programs (but not files or clickable net popups/e-mail) open just fine when double-clicked, and the files and new windows that don't open when double-clicked also don't open when I right click and select "Open". The screen looks as if it's working (a quick hourglass sometime appears), and sometimes the current window loses it's dark color (as if another window has been open/selected), but nothing opens.

Thank you for your help.

Thank you for looking into it. It is a strange problem.