This happened on my system. From the net:
“After installing the Service Pack for Exchange I ran into an issue with OWA not displaying the grahics and not loading mail content. The OWA window shows image blocks with red X’s in them where graphics should be displayed. There is a screen capture below.”

“This issue was caused by the permissions on the ExchWeb virtual folder in the default IIS website. You need to add ‘Integrated’ and ‘Basic’ authentication to the directory through IIS (see below):”

Out of Office Assistant Doesn’t Work
The “Out of Office Assistant” is a very cool feature in Exchange’s OWA. However, to get it working you need to do the following:

Open Exchange System manager
Expand Global Settings
Expand Internet Message Formats
On the right hand side right click the default and, then, click “properties”
Click on the advanced tab
Tick allow out of office
(see image, below)