MCO Controller experienced loss of separation when distracted by weather deviations in another part of the sector; believing they had issued an interim separation altitude; but had not issued any altitude restriction.

Narrative

Working a combined Arrival and Departure Sector. Weather was a factor as scattered showers and thunderstorms were causing deviations. I am recently certified on the position. I have never worked weather and deviations in this airspace. Numerous turbojet arrival and departure traffic. Several overflights. Most arrival traffic was deviating off of the STAR. With the position of the weather east of MCO; north arrival traffic was deviating east of the STAR; and southeast departure traffic was deviating eastbound. This caused my concentration to remain on one side of the radar scope as I climbed deviating departures reference the deviating arrivals. One arrival aircraft did remain on the STAR. As I was not focused on this aircraft; I did not notice how close it came to my departure traffic which was climbing from 7;000 FT to 16;000 FT. The arrival traffic was leveling off at 9;000 FT when I noticed the close proximity. Having climbed all previous departure traffic to 8;000 FT; I believe I had also stopped this departure at 8;000 FT. I did not. I tried to stop the departure aircraft at 8;000 FT; but it was too late and both aircraft passed at 2.76 miles and 500 FT.