[Chimera-users] Cannot open pdb files with older versions of Chimera

Hello, I sometimes have to use older versions of Chimera (1.2350 or 1.2422) because the more recent versions refuse to calculate surfaces for my protein. They used to work fine in my old computer running windows xp, but with my new computer (still running xp) an attempt to try any pdb files on my hard disk produces an error message (TypeError: argument 1 should be a str.). How could this problem be fixed? Your help will be greatly appreciated. Hiroshi