[isabelle] Two problems about emacs and jedit

Hello everyone,
I installed Isabelle2013 with emacs23 on Ubuntu 12.04. When I type => or \<Rightarrow>, it converts to a symbol, which looks like a very tiny "=", but not looks like a normal rightarrow. It works, but just does not look so good.
And when I use jedit, if I typed a key word incorrectly, e.g. typing "shwo" instead of "show", sometimes I can not edit the file any more. I can save the file by mous, but I have to re-open jedit for further editing. This problem also happens several times when I type "with" and "thus" incorrectly several times. 
If someone could give some assistance on these, I would appreciate it.
Thanksfor the timely help.

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