I tested my Edimax BR-6204WG router with 3 firmware: 1.51 , 1.59, 1.61.
A few problems I noticed with Edimax br-6204wg with 1.61 firmware:
1) let's say i change some setings and i chose to apply them, the wireless will go down but it will never up again, the router lights will show that the wireless is up but it's not up (tested with 3 pcs with atheros and ralink chips windows xp and ubuntu, none of them was able to connect after this cause none of them was seeing the wireless network, it doesn't matter how much I waited (i even waited 30 minutes) or what u did on the clients (scan for wireless networks, restat the os)); the only way to make the wireless work again is to power of the router and power it on
2) with 1.61 firmware the wireless seams to be limited to 1.4 MB/s (it's limited from start with only 1 client conected to it, dhcp disabled)
A few problems I noticed with 1.59 firmware:
1) it's the same as 1) from 1.61 firmware
2) strange messages in System log
Regarding 1.51 firmware witch I'm using now (I downgraded to 1.51 cause it's seams to be the best I can find) I can tell that it will restart the router from time to time without any reason (the router is on ups), after i apply the settings the wireless after it goes down it will come up, and on the wireless network i was able to get 2,8MB/s (i don't see any limitation on 1.51 firmware) (the downside is the heat, i had to put a cooler under the router to be safe (80x80 case cooler powered at 7v from an old mobile phone rechanger that i didn't needed)).
If posible try to downgrade to 1.51 firmware and see if you still have problems.
I read on other forums (romanian forums ) that some people are complaining about speed problems with 1.61 firmware.
Another thing the router i own don't look like the one here:
it looks like the one here: