Memory Issue

it doesn't run because the memory you got is quad channel, while i5-3550 only supports dual channel. So, it runs with 1 or 3 because at that point the board automatically drops into single channel mode

What?   Quad channel kit is just 2 dual channel kits in one box, it will run fine in dual channel mode with 4 sticks.

Does it run fine with 2 sticks? You said it runs fine with 1 or 3 but you didn't mention 2.

If so, have you tested that all 4 dimm slots work?

then what is the difference between LGA2011 and 1155 as one supports quad channel and other one doesn't?

Yes fine with anything less then all four.

2011 is sandy bridge enthusiast series, only this supports quad channel. More expensive cpu's, more expensive boards. Sandy and Ivy only do dual channel.

I'm aware of this, but as I understood it quad channel memory had to be different from dual channel as you don't see many dual channel ram kits claiming compatibility with quad channel cpu/board? or is there completely no difference between the ram sticks and it only comes down to CPU ability to run in quad channel as opposed to dual channel and mobo obviously has to comply?

No no no. You can use four single channel kits, 2 dual channel kits or 1 quad channel kit, as long as all the sticks are the same speed, timings and voltage it's the same.

So you can use 1 stick in all 4 slots and it works fine? I'm trying to rule out a bad dimm slot, if all 4 slots work fine with 1 stick then it's ruled out.

with two dimms in the mb run cpu-z see what the mb has set for the ram speed and timing. most time if it 1600 speed if your not using the xmp profile it drop to 1066 or 1333 speed. check under the spd tab that the mb and ram speeds are matching. also go under ram voltage..if the ram need 1.5v bump it to 1.65 and put the four dimms in and see if still locks up. if it needs 1.65 try bumping up a little. and still see if it still locks up. if it does contact intel speek with a level 2 tech and see if that ram been tested with the mb and contact the ram vendor. not all ram if you look under you mb ram guild or look at other ram guild some ram is fine for two slots..some three and some all four.