[TYPO3] t3lib_htmlmail - problem with sr_feuser_register

[Vinod S]

When a user tries to register, I keep getting this error message. Do any of
you know why I could be getting this error?

*Fatal error*: Cannot instantiate non-existent class: t3lib_htmlmail in *
/usr/local/typo3/src/typo34b2/t3lib/class.t3lib_div.php* on line *3872

I am running 4.0 RC2 and fe_user_register 2.3.0

TIA.
Vinod
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