WP3.6, W3 cache,

Hm…
Problems with output buffering may be caused by wordpress version system.
Look here

Hi Max,
Thank you for your reply!

Let me see if I understand correctly.
The Code Insert Manager is not compatible anymore with the latest WP version 3.6?

From reading your link I didn’t understand which plugin (CodeInsertManager or W3) creates the problem.

I am very unsure if I possess the skills to safely execute the solutions (manually remove cache files, optimizing my database) in your link without breaking my sites.

Hi!

The Code Insert Manager is not compatible anymore with the latest WP version 3.6?

It is compatible! I am running it on many WP 3.6 sites without any problems…

From reading your link I didn’t understand which plugin (CodeInsertManager or W3) creates the problem.

There is incompatibility between these plugins in certain situations…
Also see this thread from W3C support – the same problem, but different plugins…

… I did some seaching for this error. Looks like it is memory related. Try to increase wp_memory_limit. Standard value is 32M, set to 64M or even 128M!

I am very unsure if I possess the skills to safely execute the solutions

Unsure? Don’t do this or do on test site!

Problem seems to be solved.

I’ve set wp_memory_limit. in php.ini from 24MB to 64Mb, using FTP.

I’ve installed the “Optimize Database after Deleting Revisions” plugin and ran it, decreasing DB size by 50%.

Thanks for your help Max!

Very good! )

Woops.

It now sometimes works, not all the time.

Sometimes I still get this error:
Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0
Sometimes the page shows a blank page, without any error.

I’ve checked my host, it allows 256MB memory_limit for PHP.

I’ve set my php.ini to limit to 128MB like this in PHP.ini:
memory_limit = 128M ; Maximum amount of memory a script may consume (128MB)

I′ve set the wp-config.php to:
/** Increase memory limit for php to 128MB. */
define('WP_MAX_MEMORY_LIMIT', '128M');