I am getting this error randomly. When I restart LR everything is fine, until I get this error again. This problem has recently started occurring frequently when I exit LR during the backup. Sometimes it occurs when LR is just sitting there and I ma not interacting with it. I have not seen a pattern as to when I get the error.
My system drive is a SSD with the LR catalog and preview cache are on another SSD used exclusively for LR. My main data drive is RAID 0 with images and catalog backup to a NAS. I'm running LR 5.5 64-bit on Windows 7.
I've tried deleting and rebuilding the cache which takes a while at I have 42,000 images consuming almost 6 Tb but this does not seem to have any effect.
While this is not a show stopped, it is annoying as every time the problem occurs I need to exit LR and restart.