The fact your interface works fine under a different OS with different drivers.. isn't a clear or good indication it's not your interface or it's driver's problem.
Are you absolutely sure nothing changed? (Like an update to Mavericks for example or the installation of a new app inbetween when it did work and now it doesn't?)
Have you tried the following?
Shut down your Mac
Unplug the Pod...
Start your Mac
Fully uninstall the Pod drivers...
Restart your Mac
Delete both Logic's own prefs and the CS prefs as per this Toubleshooting Guide,... Section #8
Restart your Mac..
Install the Pod drivers (latest versions)
Restart your Mac...
Wait until your mac has fully restarted....
Plug in the Pod...
Wait a few mins.... for the Pod to be correctly recognised and setup.. If it doesn't appear for some odd reason, restart the Mac one last time....
All the restarts are essential so please follow the steps exactly as laid out.... and see if that fixes things for you.
Ok.. Further troubleshooting is needed to lock down on the actual cause...
So, unplug all/any USB/FW devices (Including HDs etc) or hubs... except Pod and test using audio tracks only (Apple Loops)
If no popping then it's an external USB device causing it so...
Next add back any USB devices, one at a time and test again..... and see which, if any, causes the issue...
if you get popping without any other USB device, it's your Pod and/or its drivers or the specific USB port you are using....... So, try strarting your mac and then plugging Pod into different USB port or Powered USB Hub.... if you have one.. (without any other USB devices plugged in) and test again....
So.. there is the clue.. If it only happens with your GX then that indicates the issue lies with the GX drivers or the connectivity to your Mac it seems... given the hardware works fine with a PC.
For this issue to suddenly happen means something has changed somewhere... be it an update in OS X... another program installed or updated or some hardware change.... or failure somewhere... or flakey drivers that have been affected by something else for some reason.
Have you checked the system logs around the time this issue began? (use the OS X Console app to take a look/see)
After a quick bit of googling I found this, which may be of interest....
Try googling Pod GX mavericks issue for more such posts and info....
All I could find is "Logtic Pro X: Audio engine overloaded resetting" - don't recall Logic crashing on me..
This is really annoying, I've got a powerful mac that I bought specifically for recording with logic and now I can't do that.
Although, I found other people experiencing similar problems when using hardware that has no drivers supported my mavericks, this seems to be not the case.
Could it have something to do with the midi keyboard that I connected ? ( I disconnect is when I use GX)