I'm thinking I'll do this, too, though I may not write many stories in the sci-fi part of it's time.

I think it depends on a lot of things...what sort of magic/cobha? Is it the kind that could be used in developing new things? Or does it provide everything people want with no effort (well, I'm sure it doesn't do that exactly, but you know what I mean...hopefully).
In
The Name of the Wind there is a magic system made of runes that can be used in inventions and stuff, I imagine that would help develop technology.
If you feel that your magic system is counter-intuitive for technological development, you could devise a way for it to be forgotten (and then maybe have it be re-discovered later on!), sort of be thought by a lot of people to be evil, or obsolete or something. And then have technology go on unhindered.
I hope I've been helpful, I'm very tired and should probably go to bed before I break something here...*turns to go and trips on an end-table knocking down a delicate lamp*
Crssshhhh!!! 
*hurries out and to bed*