Some background info, guys:
* Zen-FIre does not exist

Well, they do, but basically they wrap another technology provided by Rithmic. They seem to add a MINOR side function (getting a list of valid exchanges from their API - RIthmic assumes you know that), but all else is Rithmic. Proove? Hm, get your hands to the Rithmic API, the Zen-Fire access parameters and be happy using the Zen-Fire system with - the Rithmic API
* Rithmic is a high end system. A lot higher end than you see when you connect to Zen-Fire using either Ninja (which, incidentally, bypasses (!) the Zen-Fire API and uses the Rithmic API as it seems) or the official Zen-Fire API. Features missing (but they do work when you access them via the Rithmic API) are Microsecond timestamp (resolution 1/1.000.000) while NInja exposes only second, Subscription to complete exchange feeds with sone command (fun getting trades for about 400.000 symbols on CME alone - if you can handle that) and some more things.
* Generally, if you have feed problems with Zen-Fire and ask around, it is mostly people using it with Ninja and Ninja crapping out. Could experience that myself on a couple of occasions myself and with one another trader in my office. NInja has serious problems with fas feeds and SOME setups (T&S for example, in REAL time, they are slow to redraw, so in a fast market they start falling behind - but they offer "timed" updates there, where the T&S redrws only x times per second) or indicators - the application in the front end seems to be single threaded, which means it is prone to slow down if indicators etc. do a lot. Most end users will blame that on Zen-Fire, not realizing it is simply a terribly written front end. Many more advanced NInja users... hope they FINALLY get their act together with Ninja Trader 7.
I am trying to take Zen-Fire to the limits at the moment (well, actually RIthmic) and while we DID discover some problems with AMD processors (pending investigation - basically I get a CPU core maxing out taking the complete CME feed with all bid ask, on an Opteron 2378, while a stupid Pentium 4 can handle it with 75% cpu load - seems some code paths are bad, possibly in some third party library they use (openssl or zlib), in general it is a tremendous feed that the zen-fire / ninja combination does not even start tackling.