There are a lot of variables, like which model PDA you are using. Apparently some PDAs write to the storage card faster than others. I use an Addonics 40 GB external hard drive. I can record 24/48 without any problems. 24/96 is more of a hassle. First, you pre-allocate the files using the Live2496 file allocation tool. Then, if your files are going to be more than 4GB you have to pre-allocate several files and set up live 2496 so it automatically switches to the next file at the end of each.
CF cards work the best, but there you are limited by the ammount of storage on the card. Gordon is working on an upgrade that will allow you to switch cards while recording and not lose any of the show.