Problem with Spell Checker under Emacs

[Quito Quito]

Dear Everyone:

I use a UNIX machine (Sun Microsystems) and often use Emacs to edit
texts among other things. The spell checker works fine under
Emacs---except fairly frequently I get the following message at the
bottom of the screen when spell checking:

"Continuing spelling check using default dictionary ... "

Then the spell checking gets stuck there forever.

When this happens, I have to interrupt Emacs, and use my UNIX command
"ispell file_name.txt" to do the job.

This is pretty annoying especially when I often have to get back to
Emacs.

Would anyone like to explain what the cause of the above problem is?
How can we resolve the problem?

Thanks in advance.

Roland