There's likely one of two reasons you got gassed. Take no offense. Either you are out of shape for the event itself in which case you probably just need to ride more miles (this was a big mistake many of us made as Cat5's starting out), or more consistently (at least 4 times/week) during the months leading up to your race. You should easily be able to ride 1.5x the length of the course and should have done so several times before the race itself. I'm not sure how far, or how hard the group ride to the race reg station is, but you may not have properly warmed up. Is it safe to assume it wasn't very long (more than 10 miles) and no one was drilling the pace? If the opening climb is within your physical limits (i.e. you are not undertrained) then the pace going up should have been an intensity you had already hit for a few minutes during your warmup. Personally whatever my hardest pace will be in any given race, I will have hit that pace for 1 or 2 minutes, twice during my warmup, that is after 15-20 minutes of slowly bringing my HR up. But I'm a little older and don't do so well at 6:00am especially when it's cold out. Others do it different. If you skip whatever warmup you may actually get dropped on that climb to the race start.