RE: Recording problems with SONAR LE / Edirol UA-25
Welcome to the forum, Anwata!
Two things I want you to check:
1) If you can see the Microsoft GS Wavetable SW Synth then you're running SONAR in MME driver mode. MME driver mode is an older mode designed for backward compatbility but it is slow (has high latency) and not suitable for realtime processing or playing of softsynths. It is the only mode that gives you access to the Microsoft GS Wavetable SW Synth, but there are many alternative and better synthesizers that can be used instead with one of the two newer and low-latency modes: WDM/KS and ASIO. I recommend you try either of the other two modes and use other software synthesizers.
2) The Edirol UA-25 has three sample rates selectable by a small switch on the back-lower-right side: 44.1kHz, 48kHz, and 96kHz. In the 44.1kHz and 48kHz sample rate positions it can play and record simultaneously under software control. But in the 96kHz position there is a second switch (back-top-right side) that selects playback or recording--in that mode you have to manually select whether you want to record or playback. This device will do 96kHz but it is not a convenient implementation. I recommend you just us the 44.1kHz or 48kHz unless you really have to have 96kHz (and if you really need 96kHz then you probably need a different audio interface more suitable for the required tasks).
So, basically, switch to ASIO or WDM/KS mode and don't use 96kHz--that might help the problem you're experiencing.