I just installed Solaar to use with my Logitech K520. I'm running Ubuntu 14.04 LTS and Solar 0.9.2 Each time I reboot, I must unplug and replug the receiver, and then turn off and on the keyboard. After that, everything works great. The error message is the same one given right after installation:
Found a Logitech Receiver (/dev/hidraw1), but did not have permission to open it. If you've just installed Solaar, try removing the receiver and plugging it back in.
I get the same error after quitting and restarting the program, although this doesn't seem to interrupt the function of the keyboard. (No need to unplug, etc.)
Any ideas? Thanks