Did you update the flashcart successfully, which update patch did you use. you should update it with the latest patch:
The DSi V1.44 Patch for R4i Gold 3DS is released now! and it will be better if you can update it by DS console. And now, if you have bricked the r4i gold, you need to use a DS console and another working flashcart to unbrick the card.
instead of using a ds can i use a 3ds
Nope, you only can use a DS to do the unbrick job. Here is a guide. For example, if you have another working card Acekard 2i
1. Download the latest ak2i firmware AKAIO V1.89
2. Download the update patch which linked above, there are two files in the folder, just use the one which for updating by DS console.
3. Put the sd card and the ak2i in the ds console,
4. Power on and run the update patch, then take out the ak2i and insert your bricked r4i gold. And go on the updating process.
5 Just wait until it finishes.