Large Amount Of Errors In My Error Log File Instantly

So I wasn’t able to log in to the admin area earlier so I had to clear my cache/cookies and var files to get it to work. No big deal but I noticed the error log file was 1.5gb in size. After downloading it I erased it and almost instantly it was at 115kb in size. So I opened it up and I am seeing the following error over and over (380 errors within about a minute).

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[16-Apr-2014 17:36:22 America/New_York] PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/local/lib/php/extensions/no-debug-non-zts-20100525/ pdo_mysql' - /usr/local/lib/php/extensions/no-debug-non-zts-20100525/ pdo_mysql: cannot open shared object file: No such file or directory in Unknown on line 0<br />

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Not sure what is going on or if I should be concerned?

Host fixed it by commenting out the action that was causing the error.