Here is a link to the manual for the SMC. It contains useful information on what the status lights mean, which isn't documented in the pamphlet included in the box from Shaw. Of particular note is when the DS and US lights are both blinking, indicating operator maintenance (I believe this means the modem is retrieving its configuration from Shaw, which I saw for a couple minutes on first setup), as well as light colour indicating when you are in bond mode, indicating you have more than one downstream or upstream channels active. I think you need a minium of two downstream channels active for 100 megabit, so the 100 down 5 up is one blue light and one green light.
http://www.clitheroe.ca/misc/supportarticle2571.pdf