I am having more bugs on Fedora Core 3 than Fedora Core 2.
Among these bugs are:
1)Unmounting cdrom creates errors in KDE. Keeps saying that its already unmounted by not really.
2)The telinit 3 command doesn't return me to the login prompt. the X server is shut down but I am stuck at the message that says "Sending TERM signal to processes" or something like that. I have to press Ctrl+Alt+F1 to switch to another virtual console in order to login.
3)Mounting my usb disk crashes my computer.

I didn't enable SELinux under Fedora 2 and didn't experience these problems. When I installed Fedora 3 with SELinux on Active mode these problems occured. Is it SELinux's fault or am I just wrong for blaming it and should really be concentrating on something else? Please help.

1)Unmounting cdrom creates errors in KDE. Keeps saying that its already unmounted by not really.

Shouldn't have anything to do with SELinux. How exactly are you umounting the cdrom?

2)The telinit 3 command doesn't return me to the login prompt. the X server is shut down but I am stuck at the message that says "Sending TERM signal to processes" or something like that. I have to press Ctrl+Alt+F1 to switch to another virtual console in order to login.

Try a ctrl-d and it should go back to a prompt or login, which is normal after running a telinit 3 on most systems.

3)Mounting my usb disk crashes my computer.

Logs, learn to read or search thru your logs to find out why its causing this. More details of hardware used will help us answer these types of questions better or give some insight.

I didn't enable SELinux under Fedora 2 and didn't experience these problems. When I installed Fedora 3 with SELinux on Active mode these problems occured. Is it SELinux's fault or am I just wrong for blaming it and should really be concentrating on something else? Please help.

Most likely not SELinux's fault one bit, probably just small bugs in Fedora 3 compared to the previous version, etc.

I umount the cdrom by going into the KDE file manager and clicking eject or unmount in the context menu for the cdrom drive icon.

Thanks, the ctrl+d thing works nicely.