It comes on sometimes while i'm driving and stays on until I switch off. Then it may not happen for days.Other times it flashes on and off and when that happens the radio goes on and off

 

I know this doesn't sound like it should work but because you are losing power to the radio at the same time I would try to move the ignition key a little forward or a little back to see if the light goes out and the radio stays on. Some times the ignition switch will cause phantom problems like that.
Do it with the engine running, just don't go too far forward so as to engauge the starter.
What year is yours?

 

It's a 95 850 turbo wagon.I changed the ignition switch 2 yrs ago. I was wondering if this could be as a result of a leaking power steering pump and fluid getting into the alternator

 

If the PS pump is leaking on the alternator you might get an intermittent charge indicator or alt light. The battery is the backup that would keep supplying current to all the electrical systems even if the alternator took a complete dump so I doubt it could be any part of the problem. You still want to stop that PS leak before it does start to cause you a problem!

Have you tried to read the codes from the panel under the hood for the ABS system?

The fact that the ABS and radio go on and off together still makes me want to think you might have the new (relatively) ignition switch acting up. If you did it yourself and can do it again and it's under warranty I'd give it a try if no one else chimes in with something different.
If you can do that key "wiggling" when it's happening and it clears up, then you'd know for sure.
They are two so very different systems and for them to act up in unison sounds like it's a matter of power being interrupted intermittently going to them.
The up side of it is there likely isn't anything wrong with the ABS $$$$$
My best guess at this point.