How to get spellcheck work?

A very strange thing, I have downloaded Opera 10 build 4585 from
ftp://ftp.opera.com, the file name is
opera-10.00.gcc4-shared-qt3.i386.tar.bz2, extracted it to /tmp, enter
the directory and run ./opera, the spellcheck works, some odd words in
mail had red waves underlined.

But if I install it to /opt/op4585 by running "./install
--prefix=/opt/op4585", and run /opt/op4585/bin/opera, the red waves were
gone. Things go the same when install with .deb (debian here).

The main difference between /tmp and /opt is: /tmp is mounted as tmpfs,
it uses ram space. /opt locates in the real hardisk. Does it matter?

More, I extracted the tar.bz2 to other place in the real disk with full
write access, didn't get the red waves either.

Anyone know how it happens? What can I do to get the spellcheck work?
Any help is appreciated, thanks in advance.

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Best regards.