Stumped...Dsi stopped recognizing R4 cart

I have an R4 Revolution for DS with the Wood Firmware installed and the Acekard 2i with AKAIO.I also have two NDS units in the house: a DSi and a DS Lite.The DS Lite recognizes both carts.
The DSi does NOT recognize the R4 DS cart with Wood Firmware.Thing is, it wasn't always that way. The DSi ran both carts with no problems, until one day when it suddenly refused to 'see' the R4 DS. I never updated the firmware (still on 1.3 J). I've reformatted the micro SD card multiple times and re-installed the latest Wood firmware, but still no go.What gives? :-\

I never read where the R4 Revolution worked on a DSi, but I could be wrong. I have the R4 Revolution for my DS Lite and a R4ids.cn for my DSi and never tried the R4 on the DSi but doubt it would work for me as I'm on v1.4.4 anyway.

it depends which R4. one or two of them work on DSi