An uneven ensemble of ten improvises a group-therapy session in this dull late-night show by Chemically Imbalanced Comedy. Whenever the improv begins to fizzle, an ensemble member interrupts the scene to introduce a new idea, riffing on information gathered from an audience member before the show in the context of his or her own recollection, maybe about being a camp counselor or playing in a Christian rock band. The performers' ramblings then inspire the next lackluster bit. On the evening I attended, only one scene--about a prank played at a military base--successfully united quick thinking, fleshed-out characters, physical comedy, and silliness. And although therapists might applaud a single breakthrough in an hour, it's harder for an audience to accept such a success rate. Open run: Fri 11 PM. $8. Cornservatory, 4210 N. Lincoln, 773-865-7731.