page or post editor mode not working correctly

I installed WordPress 2.7 yesterday for a new client. When writing the first page in Visual mode, when I clicked on the “publish” button, the text automatically switched to HTML text, still in the Visual mode, and the HTML button does not work. The text looks fine to the public eye, but I want to assign this to the client for upkeep after the website goes live. At that point, the visual mode will HAVE to be working. I have read about the “WP Super Edit” plugin to install to turn off the HTML mode for the client’s use. However, I don’t want the client to see html code in visual.

I would appreciate any and all assistance. I have used WordPress for quite a while, in fact, have used it for 2 others just this week. This is the first time I’ve had this issue.