Internal Server Error: after saving menu

[Guenny]

My WordPress is version 3.2.1.
I get a 500 error after saving menu. I tried to re-update WordPress to oldest version 2.9. It didn't solve the problem.
WP-ADMIN directory have 755 CHMOD, and files in this dir are 644.

Also this code is added to wp-config:

define('WP_MEMORY_LIMIT', '64M');
set_time_limit(60);

It also didn't solve the problem.
All other things are working well.
take a look: http://www.unavitaverde.net
Help me, please!!!!

[Gandalf]

As wrote in the ticket by our technicians, there is an error somewhere in your .htaccess file.

[Guenny]

There was not the line CharsetSourceEnc in .htaccess file.
Disabling the all plugins has not helped. I solved the problem by reinstalling the old version of WP2.7. and then upgraded to the latest version.
I think there was a some conflict of plugins and WordPress v.3.2.1.
Thank you!