Been having the same problem. I did some investigating, and here are some observations:
- The particular ROM I flashed (given the timing, probably the same one you did) took up ~240 MB in the /system partition, which was ~250 MB large, leaving 10MB remaining.
- The Gapps I attempted to flash was ~15 MB, meaning that it diddn't fit. However this did not throw an error, but reported a successful completion.
Given the above, I flashed CM11, then deleted some of the larger things that diddn't look importiant. (Turns out it was emoji icons and the keyboard). This actually worked, since there was now enough space in the /system partition for gapps to copy everything over. Unfortunately, there was no keyboard.
Simply put, /system isn't large enough. My question now is if its possible to combine /system and /datadata (or whatever's using mtdblk6, seems to be ~150 MB), then move /datadata to the internal sd card, where there's lots of free space.
I'm still too new to androind stuff to know how to apprach this, but I come from a linux background so even just a pointer to the right direction would be helpful.