BO 4.1 : I received an error when I want to unmerge in my report

Hello Everybody,

I receveive this error :

[IlegalArgumentException] <pageIndex>

(Error: RWI 00011) (Error: INF )

See image in attachment

I closed my report and opened again, I swich off my session, ... Everytime that I want to unmerge my report I receive same errorImage may be NSFW.
Clik here to view.. Anybody can help me ? Image may be NSFW.
Clik here to view.

Configuration :

PC : Windows 7

Browser : IE 9

BO : 4.1

Image may be NSFW.
Clik here to view.