I have been running dd-wrt firmware on my Linksys wrt600n for awhile now however I have always had some issues. I had finally had the configuration to where the issues were minimal however it has never been perfect. I decided since it had been a couple months it was time to try a newer build from the site. I upgraded and things got a lot worse in terms of wireless on the 2.4 GHz channel so I did a ton of troubleshooting and read a lot of posts semi related to my problems with the 600N on the dd-wrt forum. During the reading I learned a lot about the proper way to flash the firmware and I wanted to share my findings here.
First off when you upgrade the firmware you are supposed to do a hard reset before the firmware upgrade and after the firmware upgrade. A hard reset should be done following the below directions.
**NOTE** Hold the reset button in during this entire process