Try forcing the upgrade by using the following command but REPLACE the "(FIRMWARE-NAME).bin" file with the one your trying to flash: sysupgrade -F -i -n (FIRMWARE-NAME).bin
Thank you for the quick reply! I apologize, I should have included that someone else (on DD-WRT Forum) has attempted that.
His reply was that afterwards it says Success, but then the router is inaccessible.
It had to be manually switched to opposite partition.
inaccessible by what means? both wireless and wired? have you tried turning the network card off and on? have you waited few mintues after forced flash? have you tried power cycling the unit once after few minutes as it may get stuck after the flash and before the reebot. if it works with the WRT3200ACM converted to WRT32X then I see no reason for the WRT32X not to flash DD-WRT. I am running DD-WRT on WRT3200X with WRT32X partition layout and u-boot myself.