Is all your ram the same name brand or is it a mixture? I had a conflict with my first batch of ram that I bought from other world computing, had to send it back for an exchange.
Not saying this will work but here is what I would do.
Since you have reinstalled and you are still having this problems, I would do the following.
1. First, I would add some more ram, add all the same name brand.
www.otherworldcomputing.com
2. Put the operating system installation disk in and start the reinstall.
3. When it loads and you go to install after the second or third window, go into the menu and select I think it is utilities, disk utility.
4. Go to the partian tab. Set it to 1 and then hit erase.
Oh ya, make sure the option is set to format for an intel mac same when you zero out.
5. When this is done, go to the erase tab, hit the option button and set it to zero out the hard drive.
6. When done, quit disk utlities and finish the install.
7. On the reboot hold down hold down
Command + Option + p + r Hold that down till your computer restarts then let go.
8. Then finish the install by going through all the Apple Information, get all the updates from apple for the operating system.
9. Once that is done install the trial version of Mac Freeze
http://www.faronics.com/html/DFMac.asp before installing Pages, Numbers, or iWeb, that way it will not stick on reboot just incase this does not fix the problem. They won't stay installed on the reboot.
10. If you do all this and add more ram and make sure that it is all the same brand and still have problems, there is something wrong with your hard drive or computer or the software that you are installing. If this fixes the problem go into Mac Freeze and set it to boot thawed on the reboot and reinstall Pages, Numbers, or iWeb for the last time hopefully.
Good luck