I also have the same problem.
I'm using the lejos 0.8.0 alpha version but seems like that this problem doesn't solved yet.
When I first clicked 'get pose' button in EV3MCLCommand.java, EV3 rotates 3 times and then below error occurs.
Exception in thread "Thread-2" java.lang.ArrayIndexOutOfBoundsException : -62
at java.lang.Thread.run(Unknown Source)
After above error occurrence, the 'get pose' button is disabled.
(I tested both ultrasonic sensor and IR sensor but results are same.)
How can I solve this problem?
Where is the '-62' value comes from?
Thanks in advance,