Oh man, I didn't see the last post by danny99, sorry for not answering.
( I had the email notifications for replies disabled..). I really hope someone already helped you out on how to fix this. However I will write the procedure step by step for others that may have this problem to see. Use these steps if the solution proposed by reykjavik in the discussion at
https://forums.macrumors.com/threads/662925/
don't work ( as it didn't work for me).
1. Insert MAC OS Disk 1 and boot your mac. Hold the C key while booting. The mac will start-up using the dvd.
2.The Language menu will appear. Choose language and proceed by clicking the arrow button.
3.From the menu bar on top of the screen, choose Utilities -> Terminal.
The terminal will open.
4. Type
cd /Volumes
and press enter
5. Type the command
chmod 755 Macintosh\ HD/
and press enter
The part Macintosh\ HD/ on the command is the HD name, that is the default. You might have changed it however so type the name of your main HD instead. It's a bit tricky to write name that has more than one words separated by space (as in the case of Macintosh HD) so to be sure, type the first few letters and press the tab key. The terminal should fill the name in the command correctly.
6. The permissions have now changed!
7. From the menu bar choose Mac OS X Installer -> Quit Mac OS X Installer
8. On the question asked click Choose disk
Choose your main HD and click restart
9. Your mac should start-up normally again
This is obviously something that shouldn't be happening so I filled a bug report to apple. Untii they fix it, don't change those permissions. Note that this problem can also come up through the file-sharing permissions as well,
check out this in the discussion at
https://forums.macrumors.com/threads/416180/
and the solution by shamino.
Cheers,
Cavas