I've been using the G15 (supposedly very similar to the Logitech G11) for ages and like it, but a few days ago I noticed trouble with the left Shift key.
When I use it in games, no problem because my left hand is further to the left, but when I type, I hit the Shift key on its upper right corner, and that causes the key to jam.
In that case, only the upper right corner of the key goes down, the rest of the key doesn't.
I contacted Logitech first who at first didn't seem to be able to read ("try turning off your computer") and then came along with warranty procedures which won't help on a 3-5 year old keyboard without receipt or even place of purchase (it was a gift...). Similar on the Logitech forum, so hopefully I have more luck here.
I already pulled the key out and cleaned it all including the wire bracket (if that's the right word), and I even tried a little WD40 - probably not the best idea, and it didn't help, in any case.
I didn't notice any obvious damage (broken bits) on the key or the keyboard.
I heard about Dry Lube and Silikon/Teflon Grease, but I thought I better ask around here, first.