Character set problem when upgrading to mysql 5.0x,suggestion needed~

Here's the scenario,it's a lil bit long:
I use mysql 4.0.16 for my working DB, one day i found that sometimes
when inserting a record into the db it reports primary key replication
error. then I found the reason for this: my primary key column stores
data which is in gb2312 charset and mysql was compiled with latin1 as
the default charset. so there's occasion that when i insert a record
with a supposed-to-be distinctive primary key,it reports the primary
key does already exist due to the charset reason.So I mysqldump my data
out and recompile mysql with charset of gb2312 and reimport the data.
BTW,when i mysqldump the data i didnt specify any charset option with
mysqldump.

now here's the problem, I see the bug report saying that there a bug in
4.0.x when using binlog try to recover the DB regarding to multibyte
characters and yes i did have that problem all the way...that's why i
needed to upgrade my mysql to 5.0.x. Does any one have any suggestion
how should I dump my data out of 4.0.16 and recover it back to mysql
5.0.x and still make the charset works? i'm a lil confused about the
charset... any suggestion is highly appreciated! Looking forward to
your answer :)