Sometimes and since a fews versions, there's an annoying bug :
when you die and are waiting to respawn, you can't spec others teammates and you don't have hud. Sometimes you can walk like a ghost in the marine start, sometimes you're on the ground in the same position as the moment you died.
It happens both in ns and co maps.

Here's a screenie taken in ns_machina while i was experiencing this bug.

This seems similar to bug 355, but the circumstances are different. I'm going to move this to Bug Investigation so that anyone with repro steps can post.

and sometimes we are like 2 marine and there is a marine alive and when i die i see the marine spawn and not the player.

this ghost mode bug like you are alive and moving but in spec mode already appeared in 3.1 but less, it seem like if you do F4 F1 it will do the bug

I havent tested this in the CM build yet, but it showed up in 3.1 on a regular basis too, so I'm guessing it probably works the same way.

Suggestion: This most frequently occurs when the entire marine team is dead at the same time--if I had to guess, I'd say it happens when you are the only marine left alive and you die, and the game attempts to find someone for you to spectate, but fails because they are all dead. So it sets your spectate differently, so you spectate the ground where you died instead. Normal behavior so far...except after another marine respawns, your spectate view will often not be reset correctly, and you will continue to spectate the ground. Even if you respawn and die again later, your spectate view is often botched for the remainder of the map.

I haven't checked if it matters whether there is still a com alive or not, although you can't spectate him anyway.

An other bug:2 Aliens die, the first respawn, and the second doesnt spectate the first he still have the free look but locked

After further review I've determined this is the same bug that Chimp referenced earlier.