Needing expert inspector advise?

I need some expert opinions here.
I live in a big apartment building, and in my bedroom the carpet gets soaked with water by the window every time it rains. The window is shut and there is no visible leaks to see. Everything on the wall and window sill appears to be dry.
But on one bottom corner of the window there is a line going from the corner to the floor and its bubbled out a bit from the wall. I think that water can be traveling down there or through the actual wall. The thing is, this has been happening for about 2 years now and I'm starting to notice the floor sags in that area, so I'm thinking it's been happening for some time now. When ever I'm in that room the floor moves under my weight, and I'm not a heavy person. It's to the point now where I'm noticing some cracks in the corners where the walls meet the ceiling. I guess what I'm trying to get at is that I think the floor may be rotting a bit and causing the walls and ceiling to crack from the movement.

Is this structural damage?
My landlord keeps brushing it off and says its nothing and all the units have cracking corners due to the fact that the building is almost 45 years old.
he refused to look at it. I just want him to come up and look at it or hire someone to inspect it. Any building inspectors out there that know anything about this type of damage? Any information would be helpful and also any poniters on what to say to my landlord to get him to get the picutre that this may be structure damage would be heplful as well.
Thanks!

You are correct in your thinking. Water is coming in from the outside (somewhere) traveling down the wall (the water mark) and into your floor and eventually into the ceiling of the person below you.

This is an issue that needs addressing/fixing by the landlord or property owner(s). You mentioned that the floor flex's/sags under your weight which makes me believe the sub(plywood) floor under the carpet has rotted to a point that it's an issue that needs fixing.

Buildings (even new construction) can have some cracking at the corners of windows and doors from settling. However your having issues with the floor/carpet becoming wet after a rain, you are noticing the cracks where the walls join.

Contact you local city building inspector if you cannot get any positive results from the owners. Document all avenues that you have tried in getting this resolved. Ask to have the inspector do an assessment of the problem and let them handle it.

Water certainly can travel inside the wall, encouraging bacterial and fungal growth that can compromise structural integrity. I would be concerned about the electric heat and the presence of water. It could start a fire even if it is not turned on, still has electrical current running to the switch on the heater.

If you can't seem to get your landlord's attention, try giving him three months notice that you intend to terminate the lease and move to a place with solid, dry floors.

First of all take some close-up pictures of the damage (2 sets). Next write a letter to your landlord mentioning the problems and the first date that you notified him. State that this is an ongoing problem and you feel it will soon become unsafe to walk in the area where the floor is weakening.
State that this leak is causing damage to paint,subfloor,carpet,pad, and may result in mold occurence.
Send this letter certified mail with a signed return receipt showing that he signed for it. *Hint - don't put a return address on the envelope as often people decline the letter if they know it's from a tenant.
What you have done is put him on record of knowing about this problem, Thus you have relieved yourself from him saying it was damaged caused by you leaving your window open, etc,etc. Some landlords would try to withold your deposit saying you did not report this problem. Keep a copy of this letter and the return receipt that shows he signed for it.
Probably 1 tube of clear 100% silicone would solve the problem by caulking around the exterior of the window.
You now have covered yourself from any damage assessment he may have had in mind.
Make a note of every time you talk to him about this problem, and note the date-time of day.