There is a simple fix for “HTTP error” message when you insert image into your post while working with wp2.5 version.
It involves inserting the following script into your .htaccess file.
<IfModule mod_security.c>
<Files async-upload.php>
SecFilterEngine Off
SecFilterScanPOST Off
</Files>
</IfModule>
Do not be frighten by this “.htaccess file” as it is really very easy to insert the script fix. Below are the steps:
Step 1. Before you begin to add the additional script into the .htaccess file, download (use a FTP program) a copy of the existing .htaccess file from your server into your computer as a backup. …

Before you decide to upgrade your WordPress version, please read my article on whether to upgrade your WordPress version or not.
If you decide to go ahead, below are the step-by-step guide on how to go about it:
Step 1: Download the latest WordPress version.
Step 2: Unzip the new WordPress version
Step 3: Backup your WordPress database in case something goes wrong during the upgrading process. I suggest that you use a WordPress database backup plugin which you can download here: WordPress Database plugin
Step 4: Unzip and upload the plugin to your …