Parallels won't start up

This is now the 5th time that Parallels will not start up. It just bounces up and down on the dock and then goes into the Application not Responding state and Force Quit will not even shut it down. I have to reset my iMac (OS 10.4.9) to get out of it.
Have downloaded 3188 and uninstalled Parallels and then reinstalled it all without any luck.
Now after the 3rd uninstall and reinstall it has finally worked again but this is I repeat the 5th time in two months that I have had to do this.
Fortunately my Virtual Machines remain intact through this trauma but why does it keep on happening and why does it suddenly work again.

 

Have you done a complete un-install? http://forum.parallels.com/thread1226.html

 

Surfway, try to this:

- reboot in Single User mode by holding apple + s keys and when unix screen shows up, type in "fsck -fy". When done, type "reboot".
- then after reboot, run Disk Utility then do the Permission fix.

Permission errors can cause applications from launching properly.

 

This can also happen if you don't have enough real memory and other aplications are opened.