It only happens when I got on the server craftedmc.dmch.nl
this is the bug report
A fatal error has been detected by the Java Runtime Environment:
#Internal Error (os_windows_x86.cpp:149), pid=6772, tid=6860
guarantee(result == EXCEPTION_CONTINUE_EXECUTION) failed: Unexpected result from topLevelExceptionFilter
#JRE version: 6.0_31-b05
Java VM: Java HotSpot(TM) 64-Bit Server VM (20.6-b01 mixed mode windows-amd64 compressed oops)
An error report file with more information is saved as:
C:\Users\Mika\AppData\Roaming\.minecraft\hs_err_pid6772.log
#If you would like to submit a bug report, please visit:
http://java.sun.com/webapps/bugreport/crash.jsp
#
AL lib: (EE) alc_cleanup: 1 device not closed
Your Java version is ancient! Please update your Java to the latest version (1.8.0_11): http://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html.*
Download the version correct for your system. If you cannot tell whether your system is 32-bit or 64-bit, please use this page to determine which of both it is: http://windows.microsoft.com/en-us/windows/32-bit-and-64-bit-windows
Please report if the issue persists with the latest Java version.