thats very interesting ( thanks for getting back )...
well... my immediate next assumption is that 'openvpn' itself may be an issue... but given few commits... and absence of any/many forum posts regarding this we can pretty much rule that out...
r16707 may have older dts/bootcode... but that probably only starts to become relevant in the context of additional connected hardware? (there were/is a few rpi kernel related patches over this time... which might also have an influence? particularly if mismatched eeprom is present?)
in this case... it seems the immediate course of action is;
- what you have done (openvpn users revert)
- wait for any/more kernel patches to filter through
- wait for other users to debug/dig into the lower levels...
out of interest... what is your current eeprom version? (and usb dongle brand/driver)