Here's what it printed for me (see artf4769 in the beta tracker)
Code:
Using Java 1.8.0_66-b18 and JRuby 1.7.17
NameError: cannot load Java class com.sun.javafx.Logging
for_name at org/jruby/javasupport/JavaClass.java:1286
get_proxy_class at org/jruby/javasupport/JavaUtilities.java:34
java_import at file:/C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-core-1.7.17.jar!/
jruby/java/core_ext/object.rb:27
map at org/jruby/RubyArray.java:2412
java_import at file:/C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-core-1.7.17.jar!/
jruby/java/core_ext/object.rb:22
(root) at C:/Users/Joe-XPS13-W7/wpilib/tools/sfx-2014.11.01/sfx.jar!/gems/jrubyfx-fxmlloader-0.4-java/lib/
jrubyfx-fxmlloader.rb:39
require at org/jruby/RubyKernel.java:1071
require at /C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-stdlib-1.7.17.jar!/
META-INF/jruby.home/lib/ruby/shared/rubygem
s/core_ext/kernel_require.rb:55
require at /C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-stdlib-1.7.17.jar!/
META-INF/jruby.home/lib/ruby/shared/rubygem
s/core_ext/kernel_require.rb:53
(root) at C:/Users/Joe-XPS13-W7/wpilib/tools/sfx-2014.11.01/sfx.jar!/gems/jrubyfx-1.1.1-java/lib/jrubyfx/
controller.rb:1
require at org/jruby/RubyKernel.java:1071
require at /C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-stdlib-1.7.17.jar!/
META-INF/jruby.home/lib/ruby/shared/rubygem
s/core_ext/kernel_require.rb:55
require at /C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-stdlib-1.7.17.jar!/
META-INF/jruby.home/lib/ruby/shared/rubygem
s/core_ext/kernel_require.rb:53
(root) at C:/Users/Joe-XPS13-W7/wpilib/tools/sfx-2014.11.01/sfx.jar!/gems/jrubyfx-1.1.1-java/lib/jrubyfx/
controller.rb:21
(root) at file:/C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-core-1.7.17.jar!/
jruby/kernel19/kernel.rb:1
require at org/jruby/RubyKernel.java:1071
require_relative at file:/C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-core-1.7.17.jar!/
jruby/kernel19/kernel.rb:24
(root) at C:/Users/Joe-XPS13-W7/wpilib/tools/sfx-2014.11.01/sfx.jar!/gems/jrubyfx-1.1.1-java/lib/jrubyfx.rb:
40
load at org/jruby/RubyKernel.java:1087
(root) at /C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-stdlib-1.7.17.jar!/
META-INF/jruby.home/lib/ruby/shared/rubygem
s/core_ext/kernel_require.rb:1
require at org/jruby/RubyKernel.java:1071
require at /C:/Users/JOE-XP~1/AppData/Local/Temp/jruby7266290731767961735extract/jruby-stdlib-1.7.17.jar!/
META-INF/jruby.home/lib/ruby/shared/rubygem
s/core_ext/kernel_require.rb:135
(root) at file:/C:/Users/Joe-XPS13-W7/wpilib/tools/sfx-2014.11.01/sfx.jar!/sfx/lib/main.rb:15
error: org.jruby.embed.EvalFailedException: (NameError) cannot load Java class com.sun.javafx.Logging