mySQL error on theme install

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I get the following error when trying to install my theme...

mysqlt error: [1062: Duplicate entry 'class' for key 'ctHandle'] in EXECUTE("insert into PageTypes (ctHandle, ctName, ctIcon, ctIsInternal, pkgID) values ('class', 'Class', 'main.png', 0, 0)")

How can I resolve this?
I am using c5.6.3.3 due to server.

trixiemay