I've noticed a few problems with invisibility and meditation being cancelled out at seemingly random circumstances, after a bit of testing I was able to find out that invisibility is broken when a player gains fame, opens a corpse, or a mob agros on the player through use of delayed/lasting spells such as explosion/firefield. Although I'm not 100% sure on whether opening a corpse should reveal the player, I do recall that moving/stealing stuff from corpses that were not your own would definitely reveal you. I have uploaded RPVs of three instances where meditation/invisibility was prematurely broken: Invisibility and Meditation breaking on firefield damage: http://www.mediafire.com/download.php?y3wg7ijo1zz2kmd Meditation breaking on fame gain: http://www.mediafire.com/download.php?11cnxyag3ercxx6 Invisibility breaking on fame gain: http://www.mediafire.com/download.php?xdgl9bqr1eu8txc Also I have noticed that some monsters are able to target you with fire breath while still invised if an aggressive action is done on them, I have uploaded an RPV of this here: http://www.mediafire.com/download.php?9ik46058bq9r75y At around 1min you can see the nightmare will firebreath the player even though he is invisible.
You should be able to remain invisible when looting your own corpse, however other monster/player corpses should reveal you. We have found and fixed a variety of other issues that break invis and meditation so its not surprising that more exist. Thanks for the report, we will look into these.