MySQLDump wrong dump
Just reading the header you put in the question shows something interesting. In fact, the question shows three things:


MySQL dump 10.13  Distrib 5.1.34, for apple-darwin9.5.0 (i386) indicates you used mysqldump from apple-darwin9.5.0 (i386) binaries
Server version 5.0.51a-24+lenny2 shows the version of mysql you used mysqldump to dump from.
You wanted to load the mysqldump file into Ver 14.14 Distrib 5.1.57, for apple-darwin10.3.0 (i386) using readline 5.1


What a jumble of versions to do this with.

If you want to see if mysqldump has an issue with the line that has DATEDIFF, try dumping just the schema.

mysqldump --no-data --all-databases ... &gt; MySQLSchema.sql


This will display ony the schema. No INSERTs will be in the output. You can then hunt down that lines. You may also want to dump the data onyl without the schema,

mysqldump --no-create-info --all-databases ... &gt; MySQLData.sql


Splitting the dumps allows you to load the schema into an editor and see if there are any problems. If you do not see any problems, load the MySQLSchema.sql into the target server. If the error is reproduced, you can fix the schema file and reload. Once the schema is loaded, you can separate load MySQLData.sql

BTW you should use mysqldump binary whose version is 5.0.51a-24+lenny2. Use dumps from version as mysqld is usually better to port and may minimize problems like this.

Give it a Try !!!