If you can try to get a 'virtual server' instead of a VPS. Like a VMWare instance, or Xen or KVM or something similar. I've found that large apps like Wowza don't play well on most hosting companies VPS offerings. Most of those offerings are for simple web servers, sometimes with a little MySQL DB server or email or other small, low-use apps. Wowza is a fairly sizable Java application and oftentimes will burn up the resources you get with your VPS pretty quick.
Of course, you can always try the developer edition of Wowza in all sorts of different places to see where it'll work. :) If you can get the dev edition to work in the VPS, it'll more then likely be perfectly fine with a licensed edition. But you may run into resource issues if you start serving out a lot of streams at once.