It's really annoying and almost lead me to change to use other CMS. I'm trying to upload a picture into Imagefield. It's like everytime I uploaded my picture, sometime it showed up correctly, sometime nothing showed up, but then, after I submited that page, the picture went away. That took me to try to upload one picture in a page for almost an hour.
Then, I started to look for the source of the problem. I started by downgrading CCK (From 1.5 to 1.4), then, downgrading Views module (Fromt 1.6 Beta 4 to 1.5). That didn't solve the problem. Then, found an topic here -> http://drupal.org/node/123977
The link above explain everything. It's a bug in Image Field module. I should have tried to upload image under Internet Explorer since this problem only happen with Firefox. (I use Firefox 2.0.0.3 and IE 7.)
I hope Imagefield will come out with a new version that already fixed this problem. Or at least, make a note in the module page so that anybody got this problem don't have to look around and took a day or two just to check which part is the source of the problem.