Ok, I think I tracked down the problem. Basically eval() will only work when the markup code is a language string. This can be fixed by making 2 small changes to ubbt.inc.php.
Line 608 and 614 look like this:
eval("\$string = $code;");
You can get rid of the errors by adding a @ sign before that line:
@eval("\$string = $code;");
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Rick Baker
UBBThreads developer