After fixing bug #826550, this problem went away. I believe it was the result of a failed sync sitting in the queue, postponing the initial delete and the initial delete raised a conflict for the subsequent delete.

In release 0.309

verified
[root@preethi-el6-pulp ~]# pulp-admin repo sync schedules create  --schedule 2012-07-22T10:30:00Z/P1D --repo-id drpm
Schedule successfully created

[root@preethi-el6-pulp ~]# 
[root@preethi-el6-pulp ~]# 

[root@preethi-el6-pulp ~]# pulp-admin repo sync schedules list --repo-id drpm
+----------------------------------------------------------------------+
                               Schedules
+----------------------------------------------------------------------+

Schedule: 2012-07-22T10:30:00Z/P1D
Id:       50103e62196f4545980022ab
Enabled:  True
Last Run: None
Next Run: 2012-07-26T10:30:00Z



[root@preethi-el6-pulp ~]# pulp-admin repo sync schedules delete --repo-id drpm --schedule-id 50103e62196f4545980022ab
Schedule successfully deleted

[root@preethi-el6-pulp ~]# pulp-admin repo sync schedules list --repo-id drpm
+----------------------------------------------------------------------+
                               Schedules
+----------------------------------------------------------------------+

There are no schedules defined for this operation.

[root@preethi-el6-pulp ~]#

Pulp v2.0 released