OPM has jurisdiction over pay and leave disputes not resolved under a collective bargaining agreement. You can find its decisions at http://www.opm.gov/payclaims/
But also be sure to check out the pay and leave decisions that the Comptroller General issued before OPM was given jurisdiction. http://www.gao.gov/search?&facets=a:2:{s:4:%22site%22;s:12:%22Publications%22;s:7:%22subsite%22;s:9:%22Decisions%22;}