I just bought the Edirol UM-1SX USB Interface. it is working okay for me except for the fact that there is a delay in response from when i hit the keys on the keyboard to when the sound iactually comes out. it is not much, but it's still pretty noticeable. i guess this would be a latency problem. I am using absynth 2 software with it, my sound card is a Delta 44.
Well, both your controller and soundcard seems okay. Make sure you use WDM or better yet, ASIO driver. Open Delta Control Panel, and set Latency as low as possible. I don't have absynth, so you need to figure out yourself on it's config.