I just found a bug in 6.5.4 Domino Web Access (DWA). One of our PC techs noticed that setting DWA to be the default mail client wasn't working. I called in to Lotus support today and got the following response after the technician researched:
"I have determined that the problem seems to lie with the 6.5.4 versions ActiveX Control. I am creating an SPR (Software Problem Report) to alert development to this issue and adding your PMR to the SPR."
I guess this will probably be addressed in 6.5.5, though it is too early to tell if it will be included in a hotfix or fixpack.