Providing you use default configuration (Explorer-style selection = Mouse only), this is expected behaviour.
The mouse click selects the file (Explorer-style selection), the Insert key deselect the file. Supposing you are on Windows 7/8, the mouse hovering on the file creates selection effect (that's Windows 7/8 behaviour). Only after you more mouse out of the file, the true de-selected state can be seen.
Last edited by martin on 2013-04-11; edited 1 time in total