Using 2.0 RC1 downloaded on 6 November 2010, I attempted to upload questions in GIFT format for both true/false and multichoice and encountered the same error with both types: "Error writing to database".
I attempted to trace the cause and discovered that the value of $feedbackformat; was the problem. If the following kinds of statements in both the truefalse/questiontype.php and multichoice/questiontype.php were changed from
$true->feedbackformat = $feedbackformat;
$true->feedbackformat = "";
then the routine finishes without any additional errors. Unfortunately, I couldn't discover exactly where the default value for $feedbackformat is assigned.