After upgrading to OS X Lion I started having a few issues with wireless connectivity to my dual band Linksys WRT610N router. After searching google it was evident that many people are having similar issues, many workarounds are suggested but they didn’t work for me.
After reading about the issues with TKIP and 802.11n I realised that this was the issue I was having. DD-WRT is installed on my router and TKIP is the default security protocol selected. Changing this to AES resolved my issues immediately and I am no longer getting the Connection Timeout error message.
I hope this helps someone with similar issues out there.