Go to:
http://www.fixmysidekick.com/sidekick-lx-or-sidekick-2008-space-bar-not-working/164/
Or just read this...:

Is
the space bar on your Sidekick LX not working when you are trying to
text or in AIM? Do you have thesame space bar button problem on your
T-mobile Sidekick 2008? Does the Sidekick spacebar work in other apps
though?
If so then this fix is for you.
1. Open the AutoText & Spelling screen. From the Jump screen,
press the MENU button, then select Settings > AutoText &
Spelling.
2. Uncheck the following settings:
-
- Highlight misspelled words
- Auto correct spelling
3. Exit out of the settings screen and try it out.
Hopefully, this will have solved your issue.
How to check for misspelled words with these two options unchecked?
Run a manual spell check on T-mobile Sidekick: To run a spell check
while in a text field from any Edit Text submenu, or by using the
keyboard shortcut by pressing MENU +S.
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