The Linksys site mentions 'Management Mode' which makes it trivial to recover from bad flashing (answer id 3176). Here's how to do it:
Unplug the power cord from the back of the router.
Hold down the Reset button.
While holding down the Reset button, plug back in the power cord to the router.
Continue to hold the Reset button for five (5) seconds. After five (5) seconds, release the button.
Wait for about one (1) minute. Then, on a computer connected to the router, launch a web browser (for example, Internet Explorer or Mozilla Firefox).
Type in the router's IP address of http://192.168.1.1 into the Address field and press the [Enter] key.
The Management Mode - Firmware Upgrade interface should appear.