Progress bar during startup - Odd Issue

Question

What's the problem:
Upon startup my iMac (early 2009, Mountain Lion) shows a grey progress bar that takes approx. 20 Minutes to complete and then the machine shuts down.
What have I done before the issue occured:
Cleaning up cache files and deleting several programms that I wasn't using any more.
What's the setup of my machine:
I have one physical harddrive that contains 3 logical partitions: One is of course the Macintosh HD (HFS+), one for data (HFS+), and one Bootcamp (FAT32) partition.
What have I tried so far:
When booting into Single User mode I ran the fsck (and fsck_hfs) command which quits after 3 unsuccessfull attempts. The only error message shown is
"Incorrect Number Of Thread Records (4, someNumber)". I tried this at least 10 times now and the behaviour is always the same, except from the number shown in the thread records message.
When booting into the recovery partition disk utility shows me the 3 partitions on my HD but shows the Macintosh HD greyed out. When checking the HD it finished without problems, when just checking the Macintosh HD it aborts with an error. Same applies when I try to fix the partition.
I tried to reinstall Mac OS but the Macintosh HD is not shown in the target disks for installation. I also tried to repartition the disk without any success.
What's odd about this issue:
First of all, I can boot into Windows (BootcamP) without any issues and work there.
Also, when in singel user mode, I can run the 'du' command which shows me all files on my Macintosh HD so the partition itself still sems to be intact.
What might be a solution:
I've have come along some comments that said DiskWarrior could fix more issues then Disk Utility but I not yet there to spend 100+ € for it.
Any other suggestions from you on how to get Mac OS back to work would be highly appreciated.

Answer 1

Thanks for your replies and proposed solutions. Unfortunately none of them worked.
@Alberto: Pressing the "D" button upon startup, does not launch the hardware test. Actually nothing realy happens for approx. 60 seconds before the machine starts the boot volume.
@Linc: I'm not able to erase the OS X boot volume as disk utility tells me it's missing it's mount point.
@romainst: As far as I remember I was still under 10.8.2. So far I have tried to repair the OS X partition at least 25 times without any changes or a chance to get this thing mounted.
I wouldn't mind erasing the Mac OS partition and reinstalling it as it only holds systems files and some applications that I could easily reinstall. Still the machine is preventing me from doing so as it will not let me mount this partition. This is becoming increasingly frustrating as the only way out seems to erase the entire HD and start over from scratch - if this is possible at all. Despite the time wasted I would also loose some of my data on the respective partition as I don't have a backup for the entire data partition.