I just received my first mikrotik gear and my configuration seems to have made it not happy. How exactly do I reset it, please? I have tried pressing the reset button both during boot up and while on but to no avail. Please help.

open terminal window:

/system reset-configuration

the button that you found is not for software reset. it loads the backup bios. software reset is a small jumper hole, see the manual:
http://www.routerboard.com/pdf/rb450GmA.pdf

Excellent, thank you. I will try shorting the hole.

As for serial, I am having no luck... all I get it garbage. I have a null modem adapter hooked to a gender changer hooked to a serial to USB cable... not sure where the issue lies. Any particular brand / model number of null modem cable to purchase that actually works out of the box?

Thanks again!
Doug

If you have the winbox configuration program, you can use it to make a connection to the device by mac address without requiring any preset IP address or the use of a serial cable.

Just plug a lan cable from your computer to the mikrotik, wait for you dhcp lease to time out then open winbox and click the three dots "..." next to the address field and i'll do a scan for the device. Click on the mac address it discovers to auto-fill the address field then click connect!

Thanks, I have successfully configured several... still have one giving me trouble... but I will try shorting the hole inside tomorrow.

Thanks again!
Doug

Here is another picture of the hole:
http://wiki.mikrotik.com/wiki/Password_reset