Ok so if you KNOW you were on the ZVC firmware prior to this little stumble, then all you should need to download and flash is the laf partition. If you are unsure, download both laf and aboot from here:
Listing of zvc_partitions (thanks to Autoprime for the uploads)
Rename the file(s) to remove the number and dash in front of the filename(s) so you end up with files called aboot.img and laf.img.
Next place the file(s) into your sdk-tools folder.
Then with the phone plugged into the pc and showing fastboot mode, change directory to your sdk-tools folder and issue the following commands:
This first one only applies if you're unsure about being on the ZVC firmware. If unsure, flash aboot by typing
fastboot flash aboot aboot.img
Then no matter what the situation, you'll flash laf by typing
fastboot flash laf laf.img
Once done, exit cmd and unplug the phone. Hold the power button for 10 seconds making sure it's powered down entirely. Now try to enter download mode by pressing and holding volume up while at the same time plugging the phone back into the PC. Report whether you get download mode now.