Recently, my webhost enabled phpsuexec on the server, and several of the web applications on my site stopped working. Movabletype began rebuilding pages with the wrong permissions, so browsing an affected page would generate a 500 error.

The way to fix this problem is to add

DBUmask 0022 HTMLUmask 0022 UploadUmask 0022 DirUmask 0022

to your mt-config.cgi file

More information on this is available at: