ACR X CLB THROUGH OCCUPIED ALT HAD LTSS FROM ACFT Y. SYS ERROR.

Narrative

I WAS WORKING THE MACON HI SECTOR IN ZTL. THE WORKLOAD WAS HVY; APPROX 16 ACFT ON FREQ WITH AN ADDITIONAL 8 DATA BLOCKS ON THE SCOPE. THE COMPLEXITY WAS MODERATE. AT THE TIME OF THE ERROR I HAD JUST FINISHED SOLVING 2 SEPARATE CONFLICTIONS THAT WERE TAKING PLACE ON OPPOSITE ENDS OF MY SECTOR. AN ADJACENT SECTOR FLASHED A HDOF TO ME ON ACR X DEPARTING BHM REQUESTING FL330 EBOUND. I ALREADY HAD 6 ACFT AT FL330 WITHIN 1 1/2 MI OF EACH OTHER ON CONVERGING RTES APCHING ATL. I CALLED THE SECTOR WHO WAS FLASHING ME X AND STATED 'STOP ACR X AT FL290 FOR HIS FINAL.' THE CTLR SAID OK. SINCE X WOULD BE STOPPED AT FL290 HE WOULD NOT BE TFC FOR ANYBODY IN MY SECTOR EXCEPT FOR AN ACFT I HAD NBOUND AT FL280; WHICH I WAS AWARE OF. I RETURNED MY FOCUS ON SEPARATING MY TFC AT FL330. APPROX 2 MINS AFTER I CALLED REQUESTING ACR X; X CHKED ON MY FREQ CLBING TO FL330. I DID NOT CATCH THIS. I THOUGHT HE CHKED ON CLBING TO FL290. ABOUT 15 MI E OF ATL I TURNED X 15 DEGS L TO SHORTCUT HIS RTE AND ENSURE HE STAYED SEPARATED FROM MY NBOUND TFC AT FL280. AS X REACHED FL290 HE HAD TFC Y ABOUT 11 O'CLOCK; 2 MI NBOUND AT FL310. NO TFC WAS ISSUED. THE NEXT COMPUTER UPDATE THE MODE C INDICATED FL295; I IMMEDIATELY ASKED X 'VERIFY CLBING TO FL290.' HE STATED NO; WE'RE CLBING TO FL330; WOULD YOU LIKE US TO DSND TO FL290. I SAID AFFIRMATIVE; MAINTAIN FL290. CONFLICT ALERT ACTIVATED AFTER I FINISHED THAT XMISSION. NOT DETECTING THAT; CHKED ON CLBING TO FL330; WAS 1 REASON FOR THE ERROR AND I TAKE RESPONSIBILITY FOR THAT; BUT I ALSO KNOW THAT IF MY INITIAL INSTRUCTIONS HAD BEEN COMPLIED WITH BY MY FELLOW CTLR THAT THIS ERROR WOULD NOT HAVE HAPPENED.