I did press the MENU button to get to the boot screen, just not at the instant I applied AC power (which, as I mentioned, never worked for me). You can hear the MENU button functioning if the 3400 is plugged in but not powered up so I suggest you do a dry run to figure out how you're going to place your finger (or thumb). Unplug the DVR for a bit, get your finger into position, then plug the 3400 in and immediately start sliding or rocking your finger to get the MENU switch to trigger. As I stated, it's a finicky process and if you get the timing just right you will see "boot" on the LCD screen of the DVR. Then use the Channel up/down buttons on the DVR to scroll through the LCD screen until you see "cold boot". Then press SELECT.
If you're too slow on the timing you'll see the 8.8:8.8 business come up on the LCD screen. (If the gods are with you the DVR might still go to the boot screen after the 8s come up but if the 8s are present for longer than a second or two then you're pooched and you'll have to start the process all over again.)
Follow protocol. Get the 1-877 number from the Eastlink RETAIL 3400 Installation Guide (NOT the guide for the rentals) and call that CSR. This will at least get your Shaw 3400 listed in the Eastlink system. In my case the 3400 wasn't responding to the hit the 877CSR sent it so she had me contact tech support at the 888 number. Since my Shaw unit wasn't responding, I forced a cold boot before calling the triple 8ers.
I cannot say if you can get away without a cold boot. The Shaw unit reacted in exactly the same manner as the Eastlink sourced 3400 that I had originally purchased (but was malfunctioning). The tech support CSR said she couldn't "see" the Eastlink retail 3400 when I called to activate it and essentially gave up. I called back the next day and the CSR I spoke with was successful in getting the Eastlink 3400 initialised. The only difference between the Eastlink and the Shaw unit when first plugged in and before activation was that the Eastlink unit would accept input from the remote but then go to 0 on the display. So, I could enter, say, channel 601, and the DVR would hold that 601 for a few seconds then go to 0. The Shaw unit would not accept any input and would not budge off of 0. Calling the 877 number removed one variable; doing a cold boot removed another. (For what it's worth, the Shaw unit came loaded with F/W 24.33; July 20, 2011.)
My warning about you pay your money and you take your chances still applies with respect to the Shaw units. I wasn't going to post at all about being eventually successful but then a chap posted in the Eastlink DCX3400 thread and made it out to be a cakewalk. In my opinion, a call to Customer Service for any reason is a veritable crap shoot. To toss in a few examples, despite repeated attempts I have never been successful in getting Eastlink's CSRs to enable the external hard drive feature on our 6416. On two of those attempts I politely and diplomatically requested access to a higher level of tech support and in both cases the CSRs refused, one of them saying, "Sure" then hanging up on me. The 888CSR I spoke with when I first tried to activate the Shaw unit told me no way no how could it be done, put me on hold for a bit then came back to say that he had spoken with several other people and none of them knew how it could be done. And that was that, until I found the 1-877 number.
Call the 877 number first to get your unit at least registered. If you need to call tech support afterward then you can try lorcaweb's suggestion and skip the cold boot and hope you get a knowledgable CSR, or you can do a cold boot before calling.