Playback Only Works Intermittenly

Lately I'm having lots of trouble playing back projects.  Currently I'm using the USB controller, the UA-1G, that was provided with the program.  Under the options, audio menu, I've tried every combination to get it to work.  When I apply the same settings that have worked in the past, sometimes I can hear playback and record my guitar just fine.  Lately though, I can't hear anything. 
Sometimes it almost seems magically it will start working - and other times the level bars move with the recording but no sound is produced.
Can someone advise as to whats going on here? My computer's information is provided below - it is a an HP laptop.
Also, how do I apply effects to my guitar sound?
Help is much appreciated.


The version of Guitar Tracks you're using: Guitar Tracks 4 USB

* The Operating System (which version of Windows) on your DAW computer (and if it's 32bit or 64bit): Windows Vista 64-bit

* Your computers processor arrangement and speed : Intel Core 2 Duo/2.00 GHz

* How much RAM your system has : 4.00 G

* The make and model of your soundcard and/or audio interface, and what drivers you're using with them