Funny crackly hiss with scarlett 8i6

[fks1]

I just got the Focusrite Scarlett 8i6 interface to record guitar using both (1/4 TRS) in line 1, and mic (XLR) in line 2. My first problem is that when i initially begin the set, i get a double delay from the mic. When i restart Live8, it goes away. Then, after using both lines for 30 minutes or so, i get this crackly hiss from the mic line. The mic requires phantom power so i have the phantom power switch depressed. I tried restarting live and the hiss went away again. Im new to Ableton (or any recording software) so my first thought is latency but if that were the case, i would think i restarting live would not make the hiss go away. My CPU usage indicates 12% if that helps.