both yui and htmlarea (Xinha) use /tmp instead of tmp?

Hello,

With a new installation of drupal 5 with the YUI Rich Text Editor I encounter the following problem.
When trying to upload an image in the editor, the yui-popup-window appears and I am able to search for a file. When clicking upload, the message i receive is a pop-up saying: "Upload Failed: Error Reading Uploaded File."

My server log says:
"[error] PHP Warning: Unknown: open_basedir restriction in effect. File(/tmp) is not within the allowed path(s): (/srv/sites/www.mywebsite.info/) in Unknown on line 0, referer: http://mywebsite.info/admin/build/block/configure/block/9
[error] PHP Warning: File upload error - unable to create a temporary file in Unknown on line 0, referer: http://mywebsite.info/admin/build/block/configure/block/9."

This same site with the same config does run on other servers.

My current configuration is (all modules with the latest version as of 11.Okt 2008):
- Drupal 5.14
- 6yui-5.x-2.4-rc2
- yui_editor-5.x-2.6-96
- upload is installed, ALL permissions are set
- folder "mywebsitename/files/images" does exist and is writeable (777)
- folder /tmp is not writable, so i changed it to tmp_00123220 (in drupal install root)

However, the upload still seems to write to the /tmp folder.

can anyone please help me?
i am at a complete loss

(oh... setting /tmp to writable is not an option)