Is it acceptable practice to run development/production servers with different versions of MySQL?

I think one issue is character encodings. I had problems going the other direction 4.0 -> 4.1.

Also, I think there is a flag for mysqldump so that the queries put out by dumping a 4.1 dayabase are compatible with 4.0.

But "they" say all sorts of crap.

I wouldn't go as far as to say it is "unnacceptable". However, from experience, I can assure you that lots of things go wrong in between pushes between dev and production -- and that's when both enviroments are identical. Having two different versions of MYSQL is likely to make things more difficult. I'd recommend against it. At the very least, set up a staging server before you push to production -- that is unless you enjoy pain.

--
"I'm not concerned about all hell breaking loose, but that a PART of hell will break loose... it'll be much harder to detect." - George Carlin
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http://www.nicklewis.org

If the main site is using 4.1, then to dump for version 4.0:

mysqldump --opt --compatible=mysql40 -v -u DATABASE_USER -p DATABASE_NAME > database.40.mysql

To dump for version 4.1, use:

mysqldump --opt -v -u DATABASE_USER -p DATABASE_NAME > database.41.mysql