Unable to upload image file using default uploader

I’ve been using the WP 2.0 default image uploader successfully since I upgraded. I haven’t made any changes at all to my WP interface or server settings. Yet when I tried to upload an image WP generated this error:

Warning: move_uploaded_file(): Unable to move ‘/tmp/phpOasATg’ to ‘/home/richard2/domains/richardsilverstein.com/public_html/tikun_olam/wp-content/uploads/2006/01/googlechinascreenshot.jpg’ in /home/richard2/domains/richardsilverstein.com/public_html/tikun_olam/wp-admin/admin-functions.php on line 1757
The uploaded file could not be moved to .

Anyone have any ideas what could be causing this? Could it be something’s changed on my server? Or some setting I need to look at internally within WP?

When I use my ftp client I see that the image displays in the file folder but has 0 bytes. I can successfully upload the image to the server using ftp.

I also note that when I write a post & try to save it in Draft that WP hangs and then the entire post disappears. Never saw this type of WP behavior before & it scares me a bit since this is the type of thing Blogger & Typepad used to do to me too regularly.

UPDATE–Bizarre stuff: I just tried uploading the image again & saving the post in Draft again & this time it worked. What could’ve happened?