If you get an error message during install beginning something like this:

# SQL=Specified key was too long; max key length is 1000 bytes:

This is probably because of your MySQL servers default character set is UTF-8 and using this encoding, every character is 16bits while others are 8bits. So, every column will have a doubled length.

You can change default character set for your tables. Open installation/sql/mambo.sql file in your favorite editor and change the string

# TYPE=MyISAM;

with exactly this:

# TYPE=MyISAM, DEFAULT CHARACTER SET latin1;

[for latin1, you may use something else]

Save the file, start mambo install again.

(Source: Mambo Forums)