I haven't used Ventrilo for a while.. But back in the day it only worked for me in BF1942 by using the CMD key (next to spacebar). When I tried keybinding push-to-talk to another key it didn't work in game.. Hope it works =).
Are you running other than your book? I can't speak for ipad but your book should work fine. I run vent on my mini (lion) just fine. I opted to use ptt rather than vox but it seems to run fine. If you like, I could check my settings and post them for you.
Could you post which computer you're running on? Should run fine on your book but I can't comment on using a pad, other than a guildie had some issues as well. I don't think he ever got it totally figured out; seemed to be flakey and couldn't reproduce problems.
If the problem persists and you are looking for alternatives I would recommend Mumble. It runs on OSX and due to the way it works it actually has less latency and better sound quality than Vent (so better for gaming!).