Today I (finally) finished my machine and did a few test cuts (Yay!). It's working pretty well with the EMC2 config that I downloaded from this site (with some changes to match my hardware). However, I'm having an intermittent problem with the Z axis. Sometimes it doesn't move in response to a G00 command. For example, sending 'G00 X  Y  Z ' moves as expected in x and y, but sometimes the Z doesn't change even though there is enough room for it to move. Instead, the stepper makes a sound that is different from the normal sound and the sled doesn't move. Might this indicate that the acme bolt is binding?
With the two test cuts of the 'EMC2 AXIS' demo, the cut depth appears to be correct, so might this simply be a problem with using G00 to move the Z axis? In case it's not obvious, I'm a complete noob at G-code and CNC machines. :)
Any advice or insights are very welcomed!