granas, have you tried starting up your mac holding down the option key? This will give you options on which system folder to start up from. If you don't get any options, you may need to come up with a Startup Disk of some kind. Another option is to connect that mac to another via Firewire...
Try dumping your Cache folder. Go to /Users/username/Library/Caches and rename it to Caches_old and restart. You might lose some minor settings in the Finder but I have found this method fixes many Apple App problems. Hope this helps. Drag and drop some old caches back in to restore some...
What was the last thing you installed before the problems started? I'm leaning towards a software issue since Safemode worked but I've seen Safemode working with bad ram before. Go to the Apple Menu/About this Mac and make sure the right amount of Ram is displayed. Let us know ...
If all else fails ... try this route: "Rip" the DVD on the PC that can read it, then transfer the VIDEO_TS and AUDIO_TS folders to your Mini. DVD Player should be able to play it this way. If you want to put it on your own DVD, I recommend Roxio Popcorn. Hope this helps.
Might be a permissions issue. This happens sometimes when someone other than admin logs on. You can get this error when you have restricted access on an account. Run "Repair Permissions" from the Disk Utility App. Hope this helps.
I have the same Headset/Mic, but USB. Does yours have the USB cable or just 2 stereo plugs? If you plug in the USB cable, OS X will see it. Go into your System Preferences/Sound and set the Plantronics Headset for your Input. Hope this helps.
I've had similar problems with my external Seagate FW drive. Turns out I had a bad Volume Header. I used Techtool Pro 4 to fix it. Depending on your budget, either DiskWarrior (which only repairs the structure of the disk) or TechTool Pro might work for you. The reason I use TechTool is if...