xlswrite not completely writing files

I'm working with some fairly large data sets, mostly cell arrays that are 250,000 rows by 256 columns. Most of these are empty, but not all of them.

when I go to write an xlsx file with xlswrite, the file gets stuck at 9kb.

any ideas what could be wrong?

[Image Analyst]

How long did you let it attempt to do the write? For doubles, that's 250000*256*8 = 512 MB - that's getting up there and it may take a while.