Question: Issues with Bases

I am trying to take out the intersection between two bases from one of the original basis. I have two matrices (A and B) and want to find the intesection between the range (or column space) of A and the null space of B. The range of A is 

X1:=ColumnSpace(A)

For some reason, the column space is not presented as a list, but with square brakes, so I convert this into a list of vectors:

X2:=SumBasis([X1[1],X1[2]])    %If I use the command Basis, it returns again square brakets, not sure why... 

The null space of B

X3:=NullSpace(B) 

X4:=IntersectionBasis([X2,X3])

X5:= X2\cap X4 % I am using latex code for the intersection symbol...

The result is the empty set! Evidently, X2 and X3 are differnt bases.

Any help would be really welcome! Many thanks!

Joaquin