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)