qgis - How to split Polygons by line grid?

I want to split a polygon by a intersecting line into different parts, exactly like in this post(Split a polygon layer with a line layer?).

I have a vector grid to cut the polygons, so I used the intersect tool(vector grid with polygons) first, to get the lines from the vector grid intersecting the polygons I want to cut.

Afterwards I followed the procedure like in the post mentioned above (union and then polygonize), but it does not provide a feasible solution, because some layers are cut as I want it and others are not.

Does anyone has any workaround about it? I read here (Making polygon from intersecting lines in QGIS using Polygonize or similar? ) that there have been some problems with polygonize, maybe this is the reason?

FYI: I am running Windows 8, 64 bit, QGIS Desktop 2.4, and installed it by the downloaded file.

Thanks for your answers!

Answer

I'd suggest to poligonize the grid and to then intersect the polygon grid with the other input polygon layer. That should be much less trouble.