Hello, from Ventrilo site, f.a.q. section :
Some games cause Ventrilo to delay sound and other functions. It has been discovered that some games, like BF1942, will consume all of the CPU time of your computer. This in turn starves other applications like Ventrilo preventing them from carrying out their associated tasks. This is especially bad for voice comm programs that run in the background and independently of any game.
In the Setup-Misc page there is an option called "Process priority class". Setting it to high could very well solve these sorts of problems. However, please be sure to read the help documentation for this option so that you fully understand the ramifications of setting it to anything other then "Normal".
Hope, it helps...