Windows – Strange problems after Windows 7 installation with Boot Camp on iMac

So, I thought give Windows 7 a shot on my iMac 20" running Snow Leopard. Installation went well, it is running without any problems. After the installation, some very strange problems occur:

1. When I boot into OSX, I have to wait for at least 5 minutes or longer, before I can login to my useraccount. I see the users on my screen, but when I click one of them nothing happens. After the 5 minutes, it's like the system awakes en everything I typed in the meantime appears.
2. It takes 2 or 3 tries sometimes before i really load into OSX. Most of the time my system freezes while loading the icons in the top, or loading the software in the dock. After 2 or 3 tries I usally make it through, and I can use OSX. While freezing I only see a colored cursor.
3. While using OSX, at unexpected moments the system can freeze, showing me just a colored cursor. Probally the same cause as problem 2. It's usally Finder or Safari that causes the system to freeze. Most of the time I have to reboot, but sometimes it works to put the iMac into sleep mode.

I thought this wouldn't be the worth the trouble, so I decided to uninstall the Bootcamp partition. But ofcourse this won't work either. When I start the Bootcamp-assistent, it states I don't have the latest firmware, although I absolutely have according to the website.

Edit: Of course, I tried to check permissions and check the disk with the installation CD and Disk Utility. I cannot check the Bootcamp partition, that one is grey, and according to Disk Utility, my Macintosh HD partition seems to be fine.

Is there a solution for this?

Edit 26-11-2010: So, still no solution. Thought I backup and format the system. No luck! Backup is also freezing.

Edit 30-11-2010: Deleted the Bootcamp position, resized it to the original format. No disk errors or permission errors. OSX is running a bit better, but all problems still occur.

Edit 21-12-2010: I am afraid this is gonna cost me a trip to the Apple Store? I was tired of the problems, so backup op important files manually, and dit a format on my harddisk, trying to re-install snow-leopard. The problems persist on the clean system. So, I did another format using the "rewrite everything with zeros" option. First time I did that the install crashed showing the "You need to restart your computer, hold down the power button" screen. Second time, it finished. Right now I am installing Snow Leopard, but almost certain that the problems are not solved, since the installation is freezing on the colored cursor I saw so many times before. Did the Apple Hardware Test, no problems found. Is this a faulty HDD or what?

Edit 23-12-2010: I managed to install Snow Leopard after a dozen tries. Are there any steps I can try before I have to turn in the iMac to a Service Center?

Edit 9-11-2011: After a long time of just leaving this problem, I started to anger me more and more, so I bought a new hard drive, and replaced it myself. The problems keep going on.. what could this possibly be now?

Just for information, the reason that I am so desperate to fix this myself, is because I can't afford to lose my computer for a few weeks, since I have no proper replacement. Also my warranty has expired a long time ago.