What do you mean by "screen flash"? Do you mean the graphical fx of the "summoning portal" opening?
Otherwise, are you sure that you are targeting a valid location? Summon spells have a limited range, and if your cursor is "aimed" at a location that is outside of the casting range, the spell will simply fail.
Another possibility is your active stone. Are you using The Atronach by chance? Because there is something of a glitch with the absorption effect of that stone, where since summon cast as "on self" casts, you absorb the cast, and it doesn't take effect, causing you to have to recast the spell.
The spell is cast normally (on the ground very close to my character) the portal sound plays as normal, however no creature appears (and my character disappears for a couple of seconds) I hadn't even chosen a stone on the playthrough.
Edit: actually, I'm using a modded save, and there is a spell absorption effect on the character [antronach perk]... that's probably it.