Unable to Save -- HELP PLEASE!!

Question

Hello all you (hopefully) helpful Mac users,
I am using a PowerBook G4 and recently a very distressing error has begun to repeat itself insidiously. I cannot save files anymore. If I begin a file in Microsoft Word, for example, hitting apple-S or selecting "Save" or "Save As..." will cause Word to "unexpectedly close." I have since learned that the only way I can save a Word document is to leave it open long enough for Word to AutoSave, then find, rename and move that copy to where I want it. As you can imagine, this is incredibly unreliable and has screwed me over repeatedly already. The same goes for all of my programs when they attempt to save a file. For example, Firefox closes whenever I attempt to download an attachment from an e-mail or saving a file from the internet, which is incredibly frustrating. I've had it up to here, and hope you can help me because I am terribly annoyed and no longer have the patience I usually reserve for my beloved Mac to bear this problem.
-jB

Answer 1

After running a permissions repair, I ran a disk verification and found that my disk does indeed need repairing. However, I am not currently near my Install disc to perform a disk repair... I will post the results of my disk verification here and ask if it is possible to repair using the 'fsck' alternative. If not, I will attempt to track down my install disc and attempt to repair from there. Thank you both for your help!
Here were my results:
Verifying volume “Macintosh HD”
Checking HFS Plus volume.
Checking Extents Overflow file.
Checking Catalog file.
Incorrect number of thread records
Checking multi-linked files.
ng Catalog hierarchy.",0)
Checking Extended Attributes file.
Overlapped extent allocation (file 4011343 /Users/a/Music/iTunes/Temp File)
4011343 /Users/a/Music/iTunes/Temp File
ocation (file %@)",1)
4014479 /Users/a/Library/Safari/Icons/13/07/2899356373-1884756597.cache
Checking volume bitmap.
Volume Bit Map needs minor repair
Checking volume information.
Invalid volume free block count
(It should be 15299667 instead of 15250472)
The volume Macintosh HD needs to be repaired.
Error: The underlying task reported failure on exit
1 HFS volume checked
Volume needs repair