I was having the same problem and after noticing my G35 headset functions weren't working I unplugged/replugged them to reset the drivers and sure enough that was the cause of it skipping. Every 10 seconds it was trying to refresh the driver and failing, causing the skipping for me. Hope this helps at least one other
I have Spotify on a Mac OSX Mountain Lion and a Windows 7 Home. Songs skip with a premium account, hardware acceleration allowed, and high quality off. Though it does skip less often when the high quality is off.
Just for streamed music. Also, I wasn't multitasking, so RAM shouldn't be an issue since both of my machines have at least 4gb. Maybe I was streaming during high traffic times? I'll try streaming during different parts of the day to see if that smooths up the playback.
If you get this every day at the same time, it could be that your ISP is shaping bandwidth at peak times. They may also be throttling P2P connections (sadly this is getting pretty common) and spotify uses P2P for music streaming. If you suspect P2P throttling, this site may help.