Mac Pro Quit mounting external hard drives

I have MacPro Mac OS X that quit mounting all of my external hd's. I've tried multiple firewire cords 400/800, multiple hard drives, different model hard drives. Nothing seems to be working. The whole system still seems to work fine and USB mounts work but no 400 or 800 firewire drives.

Any information would be very helpful. Should I be concerned that this could be a symptom of a bigger issue?

I'm having trouble with external HD's not mounting to MacPro OS X vs. 10.5.8. I've tried multiple HD's using both 400 n 800 connections. Used both 800 ports and a 400 port on the MacPro. Used different model HD's. Take the same HD's to a Macbook Pro and they mount. These drives have worked without issue on the same MacPro until this morning.

To me it seems obvious that it is device software in the MacPro but I don't know how to go about diagnosing it or solving it. Could you people help me out please before I go spend $1000 to fix it?

Please do not hi-jack someone's post. You can always post at the end of the thread or start a new thread. I moved your post here and started a new thread for you.

Run the Apple Hardware Test on your Mac Pro to see what if anything it says about Firewire. Also, have you tried running your System Information application to see if Firewire is being shown?

EDIT: Also it seems that you not only hi-jacked a thread but also cross posted. Please follow our guidelines. Thanks.

Merged your posts together here.

This is a Mac Pro with four interior hard drives bay? Are they all full to use externals which are never as fast as internal drives.

Sorry for Hi-Jacking and cross posting. I'm not on here often so I'll be sure to be more careful next time.

Thank you for your help and I will try these things to see what it says. It does have 4 internal bays. I so many files though and I work on the MacPro and MacBook Pro so I use the external drives for convenience and portability.

Thanks again.