Seems like the most likely cause is magic_quotes_gpc (thank gosh they finally decided to deprecate and get rid of this k to the rap). Check if you have it running either in your php.ini, via phpinfo(); or get_magic_quotes_runtime() (alternatively check gpc as well). If you do, turn it off, and never ever think about turning it back on (security is our responsibility and relying on the parser to do it for us is bad coding).

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