Mpok: Any information you can provide that would lead us to a fix would be greatly appreciated.
So, i've restored my old 1.2 database and tried the update again (this time, looking carefully what occured).
Note : config = MySql 5.0, converting from ISO-8859-1 on a french server.
-> all seems ok until "stage conv_tables" (so the convert_to_utf8() function works fine).
And then, the conversion of the text columns (the 'CHANGE' ... text -> blob -> text) seems somehow to REVERSE all the work done in previous stages (conv_topics, conv_posts, etc...).
This is why when viewing data in phpMyadmin the conversion seems to not have be done (and obviously the display in the forums isn't ok, accentuated characters appear as '?').
I managed to have a correct display in the forums : replacing the double 'CHANGE...' thing in convert_table_utf8() function by a single 'MODIFY... CHARACTER SET utf8'.
Now, my data are well displayed, but i'm really not sure it is a "fix"...
I will try tomorrow another test on another server (MySql 4.1.22), cause i'm thinking the problem could be related to server configuration (default charset used by the server).