503 error on login/logout only

I have a strange problem on one of my sites. When you try log via the wordpress login form it returns a “503 Service Unavailable Error” in A ‘Proudly powered by LiteSpeed Web Server’ template. The rest of the site works fine. I can login via the login form in the site. If I try login and get the password wrong it also works fine. Its only when I login via the WP login form at that I get the 503 error. Any type of logout also causes the same issue of showing the 503 error.

I have contacted the Web hosts (Webcity in Australia) and then said its not them as other wordpress sites on the same server are not having this issue. Also, when I have had legitimate 503 errors with webcity before, it using an unstyled boring looking error page – not the Litespeed formatted one that I am seeing now.

I have tried reinstalling the latest WP install via the dashboard and no difference. I have also tried checking the error logs and no related errors there.

Any suggestions/solutions???