I have two attachements, both by Thomas Conover, a Secret-Agent hud and an Avatar Online Tracker hud, I have had both of these for over two years with no problems.
After downloading the latest version of SL this morning I decided to temporarily wear a different hud but could not remove it by right clicking on it and selecting 'Detach' as the only thing that came up was the same menu you get when you right click on another avatar (this time all refferred to myself though).I expected the menu that gave 'edit' detach' 'more' etc. The only way to detach this hud was to find it in my inventory and do it that way.
I have the same problem with all my on screen huds now, which means it is impossible to move them to the part of the screen where they are less intrusive!