OK.
The wiki version where I experience the error is 2006101001 (and moodle Moodle 1.6.3 + (2006050531))
I'll wait for the wiki for 1.7 and I will upgrade the whole system (until then y avoid to insert bloks in my wikis)

But probably it is interesting to Wiki Team to know that the problem with blocks appear in WikiCourse Formar too (ot only in wiki activities). In this case, the behavior is a bit different: the course crashes when I tried to insert any wiki block (but I could change the course format, remove the block and and reuse the previous work)