My PS3 is slowing down significantly - what gives?

Hey guys, I've been experiencing trouble with my PS3 for the past couple of days, so I'm hoping you guys might know what to do.

I have a 120GB PS3 (fat model), and I've only owned it for about 5 months - brought it brand new from Best Buy in January. Well, within the past 4 days or so, just about every function of the PS3 has slowed down VERY significantly:

It takes it a lot longer to boot up.
The XBM takes a hell of a lot longer to show up after booting up.
Signing into the PSN is taking a lot longer - a good 30-45 seconds. I have cable internet, so usually signing in is almost instantaneous.
Whenever I put a game or DVD in, it takes the PS3 literally about a full minute to pick it up and show it on the XBM.
Even games are affected by it - for example, it takes about 10 seconds for my guns and inventory to load in RDR, and about 10-15 seconds to execute a command (such as getting on a horse, skinning an animal, etc).

I've been using my PS3 routinely, and I don't think I've done anything that could've harmed it. I'm thinking it may have something to do with the HDD, but I'm not quite an expert on this kind of stuff. Anyone know what might be happening? Is there anything I can do to fix it, or do I have to send it in to get it repaired/replaced?

Step 1: Be sure your PS3 is adequately ventilated and/or clean. Then try it.

Step 2: Call Sony.

Step 3: Do what they say.

Best of luck.

Well, I tried cleaning the vents, and I backed up my files and tried reformatting and such. Sadly, it's still messing up pretty badly.

So I'm going to be sending it to Best Buy. I got the Geek Squad "Black Tie" 2-year warranty when I bought my PS3 back in January, so I'm gonna turn it over to them, and they'll see if it can be repaired. If not, then they'll give me a replacement PS3.