After flapping for awhile I've appeared to successfully install Magento into httpdocs (not via the application vault).

(1) The Magento install cheat sheet says to set the following permissions:

<<Files & directories that must be writeable are:

•- file: magento/var/.htaccess
•- directory: magento/app/etc
•- directory: magento/var
•- all the directories under: magento/media
If you are using FTP, set the permissions of each to 777 or check read/write/execute for owner, user and group.>>

This did not turn out to be adequate.

After a couple of emails to Myhosting.com support I found that all folders and files need to be set to 777. (I don't know why.)

(2) After completing the install I used FileZilla to recursively set all folders back to 755 and all files back to 644 according to the following link recommended by our support people:

Magento - Wiki - Resetting File Permissions

However, the magento-cleanup.php suggested by that page did not work on the Myhosting.com server. So I did the reset of file permissions per the above (paragraph (2)).

Then I went and changed the specific folder and file permissions per the cheat sheet as mentioned at the beginning of this post (paragraph (1)).

Things appear to be working.

Jim