alt131 - 7:36 pm on Sep 25, 2012 (gmt 0)
Hi readit, and welcome to WebmasterWorld :)
Thanks for reading and respecting the forum rules, and for asking when not sure. We avoid inactive links for all the same reasons as active ones. That said, I do try to make it as easy as possible for posters to point readers to material, so as Leosghost says, feel free to contact me using the link at the top of the page to ask.
What was it that made it work - was it the vendor prefixes? Also, you've said that firebug was reporting the flexbox code as an error, but I couldn't reproduce that - can you provide more information?
Something to keep in mind is that the syntax for the flex box model has changed considerably since the first draft. One quick indicator is that the 2009 draft [w3.org] used display:box, while the 2012 Candidate Recommendation [w3.org] uses display:flex or display:inline-flex. Many of the existing tutorials/examples use the outdated syntax without noting the difference and it probably means forward compatibility issues as well as the usual backwards ones.
The CR was only made up this month so very few documents have been updated, and for fun, the "latest version" shows as either 18th or 21 September depending on how you access w3org! But MDN has two articles that highlight the difference at CSS flexible box [developer.mozilla.org] and Using CSS flexible boxes [developer.mozilla.org]. Unusually the compatibility tables don't explicitly say the vendor prefix is required, but the second article has a note about using them and -moz is still listed in the vendor extensions section (although it also refers to -ms and -o but opera doesn't have one and ie support only starts at 10).