Okay, can you take a look at this movie below, please (69s/19Mb movie, requires XViD codec (0.5Mb)).
I'm not really sure whether this is 3.0.5 hitbox related.
On the 1st clip, I shoot behind the skulk with a level 2 shotgun at close range. It shouldn't have hit at all (but I'm fairly certain that this is due to HL netcode, and is not NS-related). Nevertheless you see green blood- but the damn thing lives.
On the 2nd clip, I think this could possibly show the spark bug. During the slow-motion replay, you see that I fire my lvl3 SG right into the fades torso. All I see is a spark; but I see a bullet decal in the wall behind it. (I didn't really play enough of the last CM-only release, so I'm not sure as to whether this is considered the "spark bug".) It could just be lagging hitboxes (a server performance issue?), but I thought it best to ask for help from you guys, before 3.0.5 goes live.
[EDIT: Pause the video on 47 seconds for a clear view]
(Incidentally, the server isn't running any whacky combat plug-ins; so that skulk didn't have huge amounts of health, armour or regen.)