previously all boss runs smoothly (all the way to brutallus), now all boss give me this problem,

mods that i use is
-bongos2 (button)
-CT-raid Assist  (raid panel)
-swstats (meter)
-Omen2  (threat)
-DBM (raid warning)
-gatherer (profession craps)
-atlasloot enhanced (for linky)

pc
-p4 3Ghz, 2gb ddr2.
-galaxy gt5500 ??ddr3 ram

I have the same problem, can't raid atm. Was doing RoS in BT and latency shoots up from 500 to 7K ms latency.

I've turn off alot of my addons....... except the usual few (bigwigs, clique, decursive, sRaidframes, Omen) .. but it still lags terribly. Things was fine last week but it deteriorates last Sunday.

I'm using Gamepath too.. so it's really weird.. (pings to Gamepath server is around 300ms)..

Hmm..... I reckon I should do the same as you Boonie.. wipe everything addons off and then re-install the addons. If that doesn't work as well.. might as well stop raiding altogether

Sure.. when i get out of BT and not hv 24 ppl wait for me

well if its not the connection, er. how old is your ram? I noticed u're running a P4 and was wondering how old ur ram is. Rams do have a life span. I change my rams every year and no problems so far. Try switching with a friend who has newer rams n see. It might not be it but just check n see how old they are. It might help?

And he's going to do this during a boss fight? :?

My point is that your advice is not feasible since there is no way he'd be able to properly weed each mod out during boss fights unless 24 other players can sit there and twiddle their thumbs while someone logs out and in trying to see which mod is causing him problems.

Does your guild allow you to raid without some *necessity* mod?
Like Omen?

I dont think so.

Try this, reduce the Omen threat update frequency, it may help a bit

Ooo, great idea.. will try that.

On Addons issue, I'm one of the MT healers.. Needless to say I can't live w.o addons.
Yup, I remove WTF folder, delete cache folder, reinstall addons ..etc etc etc.. still hv high latency. Playable, but higher than usual, I'm guessing it the connection.
Ahh..it's not just at boss fight.. it was......... almost everywhere    Battlegrounds, Shattrath, 5 man instances .. O well, I only read good suggestion and turn a blind eye on those scathing yet non-useful remarks. 

P/S: Sadly, I can only get 60.54, 219.xx (EWWWW, very unstable) and 124.xx (very unstable too).    Will see if I lag again today at 25man..     .. I'll just point my finger at tmnet if lags happen again..  .. BTW it's a she..not a he.. 

I turn off Omen GUI when healing. Shouldn't be pulling aggro in single target and if multiple mob tanking for tank, then just drop in smaller heals.

And the RAM advice by noyze does help. Always a good idea to switch regularly.

OK man. I've the VERY same problem as yours. Here's the thing I did and here's the findings I got.
Like what you said, I've the same prob as you as well. It appeared out of nowhere at all, frankly it's annoying me so much, I stopped raiding for the last four months. JUST WHEN THEY FRIGGING MADE INTO MH/BT!
... fuggers..

Anyway.

Computer/UI/Addon/whatever shits.
No, it's not your computer. I believe you've done all the necessary steps in doing that one. I've gone to the extent of changing my RAM, display unit and believe it or not, changed my OS as well. Nothing, and I mean NOTHING helped.

You get DC during heavy fights. I believe your com can take in fair amount of data, sync, but during large scale pve content, there's so much data floating around, it's simply near impossible to do it. Why? Spikes.
Yeah, connection spikes. Your UI/addon furiously try to keep up with the rest of the raid, while you're getting NO connection from the server, then after a good 2~5 seconds, you get lagged out, you'll know when it happens. You log in back again, and being in mid fight, you'll get DC AGAIN, cause your UI/addon syncs with everyone else again and it's simply not fast enough. It's bullshit, I feel you on that one.

The only thing that helped for me is rewiring the home's phoneline. Yes, I'm not kidding. I now have a direct line from the phone jack outside of the house straight in. That helped the spike bits. Also, getting the right IP for it helps a lot too. 218.111.*.* works for me now. 600~700ms, I don't quite care, as long as I don't get spikes, and I dont' get DC.

It's extremely frustrating.  But yeah, it lies with your connection/line. Not your computer like the rest claims. Keep on finding the root of the prob man. Good luck! 

Computer/UI/Addon/whatever shits.

Not the way they decribed it. Lag spikes can't be helped. Even when disabled it still DOES causes the dc. Too much info such as damage and shit still goes thru. I've gone thru the extent of turning off damage reports down in the options, and no, I still get DC'ed.
No external UI, no external addons, no damage numbers.

Makes sense?

Do you use gamepath? i feel that when lots of data comes in, game path usually spikes a lot on some days, so i just turn it off. Even though the latency is 100-150 ms higher, as least there is no spike

I began with telling the OP that I suffer the EXACT same issue he did, and I said here's what I did and discover along the way. The post was directed to OP. Not your replies, wherever that might be.

Re-read the post please.
You seem to just choose what you wanna read and understand what you choose to understand... or perhaps my english writing's not up to standard these days.