Lately whenever I have nautilus open for long enough several of the options in the right click menu will become disabled when I right click on a file or folder. When I close and reopen nautilus they'll be back but it's only a matter of time until they're disabled again. The options that become gray and unclickable are cut, copy, make links, rename, copy to, move to, and move to trash (tried to take a screenshot but can't while right clicking apparently). Can someone tell me why this is happening?
ubuntu 12.04 lts
8 gb memory
amd fx 8120 cpu
geforce gtx 550 ti graphics card
1.5 tb hdd space