I was asked this question and I think the wireless reconcile option (off) would take care of this. Do you agree?

"I need to change the settings so that when I read a message on my Blackberry, the message is not affected on my desktop. I need messages to continue to be marked unread on my desktop. This is the way it was working and recently something changed and I am not losing action items."

Yes, that is exactly what you have to do. The only downfall about that option is that if you have mutliple email accounts setup on your BB, you can't choose which ones are on and which ones are off. The option affects all the accounts.

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) BlackBerry8100/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)

I use the mark unopened option, then when I get to my desktop it's still there as an action item per se. Another option I've just started using is the add to calendar or task list add on. It has helped as well.