the toolbarsmanager is on the mainform placed. if FormDisplayStyle is set to Default and the mainform is maximized then the mainform is resizing when focus is set to an other application or before a simple dialog is Shown Modal. the perfomance of the application is bad , because the mainform is resizing and redrawing everytime. if the mainform lost focus (=not active window) an small border is drawn around the mainform. Now we 've set the formdisplaystyle to Standard value. any ideas?
This sounds very similar to an issue that has been reported and fixed already. Try upgrading to the latest hotfix for the version you are using to see if it fixes your issue.
seems to be ok with 2008 vol3