Hi folks, I am playing around with Jam Origins MIDIguitar2 as a VST plug-in, in SONAR PLATINUM 
My problem: the plug in requires the latency to be set specifically e.g. 44100Hz:256 (or 128).
However the SONAR slider moves the latency in large increments. It jumps between 176 and 264.
Does anybody know a way to set the latency to a specific number?

You should be able able to type in a specific value for the LatencyMSec value in AUD.INI. This value is in milliseconds rather than samples, so you'll need to convert your desired buffer size from samples to time. At 44.1 KHz, a buffer size of 256 translates into a latency of 5.8 milliseconds. 128 samples is half that, or 2.9 ms.
 
However, I can't imagine why a device would require a specific buffer size. More likely, the vendor's recommendation is just that: a recommendation.
 

Mogus Rougus
Hi folks, I am playing around with Jam Origins MIDIguitar2 as a VST plug-in, in SONAR PLATINUM 
My problem: the plug in requires the latency to be set specifically e.g. 44100Hz:256 (or 128).
However the SONAR slider moves the latency in large increments. It jumps between 176 and 264.
Does anybody know a way to set the latency to a specific number?

Are you using ASIO (real ASIO, not ASIO4ALL)? I don't think latency settings are dictated by SONAR, but by the interface's drivers. All the interfaces I've used work in "binary" increments (64, 128, 256, 512, etc.).

MIDI Guitar does not require the setting be a power of 2 but the plug-in does issue a latency warning when the buffer setting is too high (I believe it is set to warn if over 256). The UA-25EX has an ASIO driver, have you tried using it? Or have you changed interfaces? It would be helpful to know more about your DAW configuration.