First, make sure your Logitech drivers are up-to-date. The 'check for updates' button in their software doesn't work, so you need to visit their homepage and download the latest drivers from there.
If your drivers are up-to-date, then you need to make sure that LCDSirReal is enabled in the Logitech software UI. There are two checkboxes that need to be filled; one to 'activate' and one to enable 'display on device'. For unknown reasons, these checkboxes can become unchecked after updating Logitech drivers - so doublecheck them.
If LCDSirReal is still saying it can't access the G15, check if any other plugins work. If they don't, then it's a problem with your hardware or drivers, and you should contact Logitech. If other plugins work, then you should ask for help in our forum. Don't forget to include the My Documents/LCDSirReal/errors.txt and My Documents/LCDSirReal/system.txt files in this case.
