WordPress Database Backup *Urgent Plz*

Hi…
I always do backups from phpMyAdmin but this time I tried using the backup plugin in WP … once I clicked on it I’ve got the following error ..
*———————Error1——————-*
The server encountered an unexpected condition which prevented it from fulfilling the request.
The script did not produce correct headers. It must at least print out a Content-Type header, like so:
Content-Type: text/html

The header the script produced was:
charset
*———————Error1——————-*

the same error comes every time I try open any page in my blog …. then after I deleted this plugin from the plugins folder .. it worked … but came up with another issue ??

Whenever I try to attach a file in the writing page I get the following error
*———————Error2——————-*
WordPress database error:[Duplicate entry ‘0’ for key 1]
INSERT INTO blg_postmeta (post_id,meta_key,meta_value) VALUES (‘0′,’_wp_attachment_metadata’,’a:4:{s:5:\”width\”;i:714;s:6:\”height\”;i:230;s:14:\”hwstring_small\”;s:23:\”height=\’41\’ width=\’128\’\”;s:4:\”file\”;s:77:\”/hermes/web03/b414/pow.alkaboosx/htdocs/blog/uploads/2007/02/winup0111.GIF\”;}’)

Warning: Cannot modify header information – headers already sent by (output started at /hermes/web03/b414/pow.alkaboosx/htdocs/blog/wp-includes/wp-db.php:105) in /hermes/web03/b414/pow.alkaboosx/htdocs/blog/wp-includes/pluggable-functions.php on line 270
*———————Error2——————-*

then I tried to just add a new post without attachments but I got this error
*———————Error3——————-*
WordPress database error:[Duplicate entry ‘0’ for key 1]
INSERT INTO blg_postmeta (post_id,meta_key,meta_value) VALUES (‘0′,’_pingme’,’1′)

WordPress database error:[Duplicate entry ‘0’ for key 1]
INSERT INTO blg_postmeta (post_id,meta_key,meta_value) VALUES (‘0′,’_encloseme’,’1′)

Warning: Cannot modify header information – headers already sent by (output started at /hermes/web03/b414/pow.alkaboosx/htdocs/blog/wp-includes/wp-db.php:105) in /hermes/web03/b414/pow.alkaboosx/htdocs/blog/wp-includes/pluggable-functions.php on line 270
*———————Error3——————-*

BTY, I’ve checked my log file when I got the first error and found many lines like this
*———————Error4——————-*
PHP Warning: Zend Optimizer does not support this version of PHP – please upgrade to the latest version of Zend Optimizer in Unknown on line 0
*———————Error4——————-*

What I have to do ??????

Thanks in advance