My Matshita sr-8584a dvd rom drive has locked and will not play any dvd's at all. Do I need to download new firmware to unlock it and get it working again? I never set the region permanently and don't want to go and have to buy another drive> Heeeellllpp !!!

If it's locked, then someone set the region. You will probably need to flash with a patched firmware or else use software like VideoLAN or DVD Region Free.

Find the firmwares here: http://forum.rpc1.org/dl_firmware.php?download_id=108

The Matshita sr-8584a has extra protection, that "DVD Region Free" cannot handle. (DVD Region Free web site specifically mentions it.) VideoLan might not do any better.
I got my "Matshita sr-8584a" a long time ago as a RPC-1 drive, so I never had to flash it.
See below for details of it under linux.
So if you make sure you have e15c firmware, you will not have any region problem.
I expect the firmware to be out there on the internet, but if not, I could probably find out how to read the firmware off mine and email it to you.

hdparm -I /dev/cdrom

/dev/cdrom:

ATAPI CD-ROM, with removable media
Model Number: MATSHITADVD-ROM SR-8584A
Serial Number:
Firmware Revision: e15C
Standards:
Likely used CD-ROM ATAPI-1
Configuration:
DRQ response: 50us.
Packet size: 12 bytes
Capabilities:
LBA, IORDY(can be disabled)
DMA: sdma0 sdma1 sdma2 mdma0 mdma1 mdma2 udma0 udma1 *udma2
Cycle time: min=120ns recommended=120ns
PIO: pio0 pio1 pio2 pio3 pio4
Cycle time: no flow control=120ns IORDY flow control=120ns

Could you tell me how to read out from the new combo's firmware and update it to the restricted region one? because my nec cb-2100A can't find any firmware on internet!
thanx a lot.