It looks like somehow the bar style definition has gotten corrupt. Create a new bar style for summary tasks and it works fine.



By the way - you should not have resources assigned to summary tasks.

JulieS, thank you very much for prompt reply! Actually your reply made me "play around" a bit more with rolling up tasks and I discovered that if I click on a specific point on the main rollup summary bar, I can make it work! That I did not know really, that I actually have to click specifically on the black line bar which is visible during weekends..! Many thanks again, you opened my eyes! :-)