If it isn't the pads, or the sliding parts then it can only be a hydraulic pressure issue - it cannot be released fully as fluid can't return to the master cylinder.

As a few people have mentioned, first check the master cylinder isn't over-filled.

The next thing to consider (and its quite easily done) is that in the process of changing the fluid and bleeding the system you've turn the master cylinder seal inside out, or dislodged it allowing fluid to pass out but restricting its return.

Lastly, and this is quite rare, the hose might be breaking down internally and allowing fluid to pass only one way. I've come across this three times, twice on bikes, and the last time only a month ago after changing the clutch on my Land Rover...

I replaced the master cylinder and slave cylinder along with the clutch only to find (with everything set up right) I couldn't get any free play and the clutch slipped all the time. Fluid was moving under pressure to the slave cylinder but not returning to the master cylinder keeping pressure on the clutch release bearing. Very similar symptoms to your brakes, but with a hydraulic clutch. Changed the flexi-hose and all was good.

What happened was the hose had broken up inside leaving a flap of rubber partially blocking the bore. This flap acts like a one-way valve stopping fluid returning to the master cylinder. Sometimes you get this and the "flappy" bit works one way, sometimes the other and sometimes blocks the hose completely.

Are your hoses original? You are aware you're supposed to replace them every 3-4 years for exactly this reason.

__________________