Seems like one big problem, I really could use some help!

Tried another driver, same problem, identical. I'm sweating cold here.

First, don't panic .... you'll get it working most likely. You are just learning how to do it first time right?

YOU MUST check every solder joint for continuity and shorts, that is your problem here. do you have a multimeter? if you don't, grab one, a cheap one will do ... are your leds on stars? they are connected in series right?

I have bought a multimeter before, but I have no idea on how to use it. I have it on my lap atm. What am I looking for on each solder joint? I'm afraid the blinking is some kind of safety measure. I can hear a very low "tick" coming from the driver when the 4 lights flicker. So I should turn it on briefly just to test and stop at each 5 seconds or so? I'm trying not to panic but this really pissed me off.
Yeah, first time! And I just discovered I might not be very good with a soldering iron. Mine is 25w, though - is that enough? too much?
I feel dumb for not even having the slightest idea of what's wrong. Everything seemed fine, I didn't take more than 5 seconds to solder each pole, I really don't know.

25w is a bit low but you should manage!
don't need to use the driver for testing the joints, turn the unit off and use just the multimeter!
there is a function on the multimeter that is "test diode" function:
Digital-Multimeter.jpgsee that one? set it on that one! Now with the two cables, one inserted on COM the other on V mA, check every single diodes first, than check the joints placing the two cables at the end of each wire connected to the single diode that you are testing. Hope that's clear, hang on let me see if I can find somewhere with a video .......

right go here: http://marine-engineers.org/2012/03/...eds-in-series/

there is all you need for your solder joint tests! let me know!

All the red leds lit up very dimly, all normal except for two that were a little dimmer. (no. 3 and 4)
Blue and white leds didn't light up at all. I'm using the black cable for - and the red cable for +;
Checking the joints now.

When I power the driver on, the last led of the cascade is blue and it lights up "normally" (Flickering like the first three).

Ditto for the joints. No response on the blue or white ones, a slight dimming on the 3rd to the 5th led.

check them meticulously before assuming some diodes don't lit, sometimes the cables don't stay in place nicely!

I tried all blue and white ones across my chassis, even the ones I haven't wired yet, and none of them light up... but I'll try again.