I have this problem on WordPress 2.6.2 with a MySQL version 5.0.32 backend. PHP is version 5.2.6 and its all run on Apache on an Debian server.
I’ve checked that the folder wp-admin/import is available and contain the right files. Folder and files seem to have correct permissions/rights (compared to a working installation).
I’ve also tried to disable all plugins (both through the management interface and by renaming the original /plugins folder and creating a new, empty one) to no avail.
Any additional help would be appreciated since this is annoying!
Brgds