I compiled the latest 2.6.0 SVN with no modifications.
The Minimize menu options in Spark display as "iconify". (Clicking top left Spark icon and the top right Minimize button.)
I'm running the Windows version of Spark 2.6.0. Compiled with Netbeans IDE 7.0.
I'm not sure how to fix this. Its a very minor bug. But it should be corrected.
My system config:
Windows XP x86 SP3
Latest Java JRE/SDK
Latest Netbeans IDE 7.0