[TYPO3-english] sr_feuser_register and sr_freecap problem

[Cray Flatline]

Last time i have many fake registrations on my site, so I decided to
setup captcha to registration page. I have installed sr_freecap and set
added subpart to sr_feuser_register template. But image doesn't appear.
I tried to access to image directly:
http://domain.com/typo3conf/ext/sr_freecap/pi1/captcha.php?id=49

and I see such message:

NO entry in the $TCA-array for the table "tt_content". This means that
the function enableFields() is called with an invalid table name as
argument.

Please, help me, because I'm not so familiar with Typo3 to understand
where is the problem?

Can I somehow use another captcha extension with sr_feuser_register?

--
WBR,
Cray Flatline