General Support: Cache - Solution for my Web site gallery

Hi the best gallery script plogger forum members and peers,

I have been frequently getting the empty space as well as internal server error. I have complanined to my host and they suggested to find the cache solution for my site plogger gallery (entire converstations is available here - http://www.netgana.com/site_error/ )

I have searched in net and I have found one solution from here of using php buffering to cache the php page
(http://simonwillison.net/2003/May/5/cachingWithPHP/ ) - I have applied this code on top of index.php.(http://www.netgana.com/actress/ - It is working some time but some time it is giving the blank space and i have checked in error logs it is keep telling this....

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PHP Warning: fwrite(): supplied argument is not a valid stream resource in /htdocs/actress/index.php on line 16
PHP Warning: fopen(cache/index-cached.html) [<a href='function.fopen'>function.fopen</a>]: failed to open stream: No such file or directory in /htdocs/actress/index.php on line 15
PHP Warning: Cannot modify header information - headers already sent by (output started at /htdocs/actress/index.php:18) in /htdocs/actress/plog-load_config.php on line 26
PHP Warning: session_start() [<a href='function.session-start'>function.session-start</a>]: Cannot send session cache limiter - headers already sent (output started at /htdocs/actress/index.php:18) in /htdocs/actress/plog-globals.php on line 5
PHP Warning: session_start() [<a href='function.session-start'>function.session-start</a>]: Cannot send session cookie - headers already sent by (output started at /htdocs/actress/index.php:18) in /htdocs/actress/plog-globals.php on line 5
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Here I need help from you is....is this code what i am using is correct ? or If you need to alter this code in order to not get these errors...kindly help me...as I am not good in PHP and not a techie guy.

Thanks in advance and please help.

Regards,
Gunny007