OSX Yosemite: I can not move the icons on my display. They always jump to an other position

Question

Hello,
I updated my OS X to Yosemite last week.
First problem: Since then, I can not update several applications any more. Yestersday, there where 5 updates: iMovie, iPhoto, Keynote, Pages and Numbers. iMovie and iPhoto updates were ok, but for the other 3 I received a message ""Update Unavailable with This Apple ID.This update is not available for this Apple ID either because it was bought by a different user or the item was refunded or cancelled"". As far as I know, I was never refunded, or I never cancelled an app that was originating from Apple. I even don't know how to di it !!
Second problem: I can not move any more the icons on my display. And sometimes thy are moved to an other position after start. For example: the Mackintosh HD and the external Time-Maschine HD were always in the right upper corner on the display. This morning, after starting, they were in the left lower corner!! No way to slide them back to the other side. They always jump back to the lower left.
HEEELLLPPP !!

Answer 1

Hello,
Performance tip: Keep the Desktop clutter-free (empty, if possible) by: Klaus1
Mac OS X's Desktop is the de facto location for downloaded files, and for many users, in-progress works that will either be organized later or deleted altogether. The desktop can also be gluttonous, however, becoming a catch-all for files that linger indefinitely.
Unfortunately - aside from the effect of disarray it creates - keeping dozens or hundreds of files on the Desktop can significantly degrade performance. Not necessarily because the system is sluggish with regard to rendering the icons on the desktop and storing them in memory persistently (which may be true in some cases), but more likely because keeping an excessive number of items on the Desktop can cause the windowserver process to generate reams of logfiles, which obviously draws resources away from other system tasks. Each of your icons on your desktop is stored as a window in the window server, not as an alias. The more you have stored, the more strain it puts on the window server. Check your desktop for unnecessary icons and clear them out.
Keeping as few items as possible on the Desktop can prove a surprisingly effective performance boon. Even creating a single folder on your Desktop and placing all current and future clutter inside, then logging out and back in can provide an immediately noticeable speed boost, particularly for the Finder.
And it is why Apple invented 'Stacks' for Leopard.
Keep your Desktop as clutter free as possible!
Carolyn