Turn off your Firewire device then do this:
Step one:
Right mouse click on the "my computer" Icon

Step two:
Choose "manage" from the drop down list

Step three:
In the "Computer Management" Window choose "Device Manager"

Step four:
On the right - hand side of the window. Look for the entry "IEEE 1394 Bus host controllers"

Step five:
Click on the "+" sign to the left of the IEEE 1394 Bus host controllers entry

Step six:

Select ( left click on:) ' Texas Instruments OHCI compliant IEEE 1394 Host Controller to select it

Step Seven:

Right mouse click on it and choose "Uninstall"

Step Eight:

You will get the "Confirm Device Removal" box.... Hit the "OK" button

Step Nine:

Restart your computer...

Turn on your firewire device(S) and test.