New computer wont start deja vu

Oldest problem in history but I have some "new" questions so I dared to post...

What has happened:
I put it all together and I got it working.
Just changed the CPU cooler and started to get nasty odor and in one occasion blue sparks (this happened while I was trying to power up using another power unit).
Got the MB changed and now everything is just dead. Got a little click when power switch is pressed.

I suspect that the casing is short circuiting (possible)?

Now, I have put together dozen or so computers over the years and I admit there has been couple of years since I built my last one. But... I read the manuals, remember to but the power on etc. And everything has always been sorted out by testing and changing parts.

Can I power up the the MB without it being attached to the case? Does it need to be grounded (is that even the correct term?)

Components:
SSD drive
Intel Core i7 2600K
2x2 Kingston Valueram
Seasonic X-400 400W power

Since it started once I wonder if I blew the power supply also?

Thanks for any replies

 

Ok thanks... maybe I just try without the casing first.
Unplugging all cables, to try with another psu, is going to a b**ch since it is a tight casing and all cables are individually placed to ensure that nothing gets in the way.

Would it be sufficent just plugging the main 24pin connector and the extra 4 pin power while other cabels still remained attached to my older gear?

 

Well I plugged the wires and hit power:
There was a miniature sun on the MB!

Since this is the second motherboard and straight from the store and reaction so violent I doubt I did something wrong. Lack of time has prevented me to study more closely the PSU I used but I'm quite sure I'm not gonna find another 4-pin connector that would fit to that additional power slot. So I'm left to wonder what I did and until I get another MB I don't have a chance to test further.

Sigh