I thought that this was a problem only for version 2.8 but I just ran into it... I installed my wordpress manually and everything works, but when I try to load .zip theme files this is the message I get:
Incompatible archive PCLZIP_ERR_BAD_FORMAT (-10) : Invalid archive structure
I tried overwriting http.php with other versions but it didn't help, I've changed it back to the original now.
Any help greatly appreciated!