See MC-68754, it's the same problem.
The problem exists in 1.8.2-pre5 & pre6, everything works fine with 1.8.2-pre4 on the same system
Environment
Windows 8.1 64-bit, 1.6.11 Launcher, Java 1.8.0_25 64-bit
MC-77053
Exiting Fullscreen Disables Maximize
Resolved
Duplicate
0
Reopened MC-68754