Random admin page load issues – mostly editor-related

Hi all. This was a bit of a problem with the previous version, but with 2.9 it’s pretty much keeping me from posting much at all.

When I load the Edit Post page, I get a number of intermittent page errors. Sometimes the editor can’t switch, sometimes the text in the visual editor is invisible, sometimes it’s displayed as HTML (and sometimes as expected). It’s not predictable.

For example, I load Edit Page and Firebug tells me…
* “edToolbar is not defined”, “jQuery is not defined”, “tinyMCE is not defined”, and “tinyMCEPreInit.go is not a function”
* Ctrl-F5 and I only see “tinyMCE is not defined”, and “tinyMCEPreInit.go is not a function”
* Ctrl-F5 again and this time it’s “getUserSetting is not defined” — and trying to switch editors yields “switchEditors is not defined”
* Ctrl-F5 again and now it’s edToolbar, jQuery and getUserSettings (but not the tinyMCE stuff)

Ctrl-F5 again and everything loads perfectly until I go to add media — then I get two “jQuery is not defined” and a “SWFUpload is not defined.”

In any case, I haven’t been able to use the flash uploader since I upgraded. (Clicking it simply does nothing.)

I also sometimes get the jQuery error on the main admin page, and IE often reports “Expected ‘;'” in load-scripts.php. F5 and it’s better. F5 again and it’s back.

I’ve tried 3 browsers, 3 computers, disabling all plugins, automated reinstall, downloading/FTPing wp-admin and wp-includes, clearing browser caches, restarting browser, clearing wp-content/uploads/js-cache. Now I’m suspecting that my host has problems serving up files. If so, how can I tell them what needs to be fixed?

Any ideas? Any hints would be greatly appreciated!