The :/usr/share/phpMyAdmin is not in the open basedir path yet according to the error log. This can have several reasons:
a) You did not wait until the files had been written to disk. wait at least one minute. You can check if there are open tasks in the jobqueue of the ispconfig monitor.
b) The :/usr/share/phpMyAdmin was added to the wrong website. If you are not sure which website this is, add it to all websites.