I seems these routers use VxWorks operating system instead of Linux operating system. (DD-wrt uses Linux.)
That's why they can fit into 2MB of flash - that saves Linksys a few pennies per router.
The flashing process requires upgrading the VxWorks software for the router with a fake VxWorks or a VxWorks-killer. After that step people can flash in dd-wrt.
You probably know all about this since you successfully got dd-wrt on your router.
Somehow this VxWorks killer process needs to be reversed - though I must confess I do not know anything about it.
Sounds like BS only disclosed how to flash these V8 routers this month.
A procedure to take them back to factory linksys firmware may not have been worked-out yet.
As I have said before - people experienced with your Linksys router are much better suited to helping you. They must all be out having fun on this fine Saturday.
Maybe they will show up this evening and try to help you?
If you end up needing to replace your router, I recommend the ASUS 500gP or 500W. The W does the new emerging N standard. I own the 500gp. Both models have 8MB of flash memory. DD-wrt uses 4MB, and that leaves 4MB for JFFS space for loading extra goodies. Both models have 32MB of RAM memory - so I have plenty of memory for extra goodies like milkfish, and I don't worry about the memory leaks - I auto reboot once a week. Also, many people like the Bufallo products - they have the reputation of very strong wifi, though I think most don't have as much memory as the ASUS.