My last one started out pretty slow, too. In the first fifty pages I had um...MC breaks into building, gets caught, manages to escape (has to fight his way out), there's a big explosion. That basically covers the first chapter. Up through page fifty would have some random dialogue (not really random, but you get what I mean) with two of the other important characters, finding out a girl is dead, and my MC deciding to go off and warn another girl she might be next. I think 50 is right before he actually meets her and talks to her.
If we're talking first 3 chapters (which is about 96 pages for me), there's a bit more involved. MC convinces said girl (against his friend's wishes) to go with him, one of his partners reveals some important info about his past, they try to change girl's appearance to make her harder to find, and my MC has a fight with a friend to convince him to go threaten a guy to get a code they need. That's about it, though.
My current one doesn't have fifty pages yet, but I suppose right now it's a bit slow, too. Narrator goes to work, almost gets shot, has to bandage up one of the other MCs who was injured in a fight, um...what else has happened? Oh yeah, introduce the other main MC, narrator commiserates over drinks with a friend, and I'm pretty sure he's going to be kidnapped within the first fifty pages.
Personally, and I know a lot of people will disagree with me on this (particularly considering that a lot of people actually flip through books before buying them), but I've always felt like a book should build, and that's what I tend to do in mine. I guess it goes back to junior high and learning the whole rising action, climax, falling action curve, and I tend to pace to fit that. Things move faster and faster and build up to the climax.
Anyway, my opinion is probably pretty meaningless lol, especially considering my current epic fail with submissions on my last MS (wee form rejections!)*.
*to my credit, I haven't heard back on that many yet...