The error is most likely to the fact there is variable called dir (or, less likely, length) in your workspace. Try this
which dir
which length
To reproduce the error:
clear dir
dir('*.*')
dir = 1:4 ;
dir('*.*')
which gives the error " ??? Index exceeds matrix dimensions. ". The reason is that the last line is looking for the 42nd element of the vector dir, which has only four elements. (the ascii code of '*' is 42).
