CH340G Driver Problem On Mac

I have a Mac running 10.6.6. I have 2 different Uno clones with the CH340G chip on them (the boards have different printing and appear to have been made in two different places, one came with blink preloaded so I have no reason to think they're both bad.) I've tried different USB cables. I have installed and uninstalled every version of the CH340 driver that I can find - originally the one from wch.cn, but since then several versions from other blogs addressing the problem and links on this forum, and most recently the package from codebender.cc.

No matter which driver is loaded, when I plug in either board Console displays the following:

1/28/16 10:38:14 AM com.apple.kextd[10] /System/Library/Extensions/usb.kext - no compatible dependency found for com.apple.iokit.IOUSBFamily.
1/28/16 10:38:14 AM com.apple.kextd[10] /System/Library/Extensions/usb.kext - no compatible dependency found for com.apple.kpi.iokit.
1/28/16 10:38:14 AM com.apple.kextd[10] /System/Library/Extensions/usb.kext - no compatible dependency found for com.apple.kpi.libkern.
1/28/16 10:38:14 AM com.apple.kextd[10] Can't load /System/Library/Extensions/usb.kext - failed to resolve dependencies.
1/28/16 10:38:14 AM com.apple.kextd[10] Failed to load /System/Library/Extensions/usb.kext - (libkern/kext) dependency resolution failure.
1/28/16 10:38:14 AM com.apple.kextd[10] Load wch.usb.usb failed; removing personalities.

I've spent a great deal of time googling various words and phrases associated with these errors and I can't find anything that's helped. Someone has been through this and figured it out before, right? Any suggestions would be greatly appreciated. This has been driving me crazy for days.