USB causing crashes

Question

I'm trying my best to keep this short!
I've been using my Mac Pro for a few years now without any problems. Recently I moved it to a building that doesn't have an internet connection, so I use my wife's extra Sprint USB mobile broadband card. From time to time, I would unplug/plug it from the USB on the back of an old 17" mac monitor, to move it to a nearby PC. Anyway, things were fine for a while, but a few months after using it, I was plugging it back in to the USB hub on the back of the monitor (after having it in the PC), and the computer freezed IMMEDIATELY after plugging it in. I do have a lot of USB/firewire peripherals, but at the end of the day, the problem started with plugging in the Sprint card. After this, it was continuous crash after crash.
I ended up doing a total clean install of my system because things were becoming such a hassle. I was stupid and continued to use the sprint card after everything was back to normal, and I'm back to the crashing. I've had to force shutdown about 5 times, and I don't want to do it anymore (The last time I did this, I ended up having to do manual shutdowns about 10 times and the HD and RAM DID survive, so I'm hoping it will be a trooper again and not be physically damaged).
Is it at all possible that I have somehow damaged the USB system on the computer? I have a 4-port PCI express card, too.
As far as the current series of crashes -- I will NEVER plug that sprint card into the computer again. now, I need help just getting the computer so that it won't crash a few seconds after loading the finder and/or freeze during the boot.
I want to do a system check from the startup disc, but I need to actually get the DVD INTO the computer -- but it's crashing... what do I do? I can startup in safe mode, but it crashes fairly quickly. Holding down C at startup either leaves it frozen with a blue screen, or crashes just after the dock/finder loads. any other advice on getting things stable?

Answer 1

Here is my recommendation on shopping list and brief tutorial.
Try setting up a couple new hard drives.
Pull the old one for now at least.
Drive #1 main system
Drive #2 600GB backup, 35GB emergency system
Drive #3 data, media files and libraries
Drive #4 scratch if needed, and TimeMachine
Buy SuperDuper or use Carbon Copy 3.3
Buy Alsoft Disk Warrior or another top utility for disk and system maintenance and repairs.
Your current hard drive is corrupt to the point you can't boot from anything or do anything. So the directory and catalogue and probably journal file are "shot" and can't repair itself. May also have bad sectors.
USB modems I know don't work well if at all in Mac OS.
USB cables can cause shorts or electrical anomalies, more often seen as a kernel panic
Instead of the monitor, why not direct USB port? or off your PCIe USB card that it sounds like you added?
When things are "normal" is when you want to make a backup image and keep it for safe keeping.
An actual disk image; a volume image or clone.
A "working" backup with the latest changes.
An emergency system partition that you never use except for maintenance (make a backup image of it too for safety)
Run Disk Warrior etc on a regular basis before there is trouble as preventative maintenance
The Sprint USB broadband replacement I'll leave for someone else that knows what works that you can install.
http://support.apple.com/kb/TS1388
http://www.thexlab.com/faqs/faqs.html
http://www.apple.com/support/leopard/internet/
Bad sectors, bad news
http://www.thexlab.com/faqs/repairprocess.html#Anchor-Bad-11481
resolve kernel panics
http://www.thexlab.com/faqs/kernelpanics.html
Guide to troubleshoot and isolate issues, as well as k/p
http://reviews.cnet.com/8301-13727_7-10344626-263.html