unknown error when trying to save

Hi

I am using Illustrator CS and am working on a large mural - it will be 14.6 metres long (file is set up one tenth the size). After flattening all transparency I am not able to save the file - I get an unknown error message...

If I do not flatten the transparency the file prints with artifacts/pixelization in areas where there are multiple layers of transparency.

Have tried saving as an AI without PDF compatibility, also as eps, but still no luck.

If anyone has any suggestions I will be most grateful.

the pixel doesn't have to be from the transparent layers, it could be different in resolution like using low res photos. i worked on 60page book that full with different transparent photos and layers, and didn't pixelate without me using the "transparency flattener presets".

some fonts can't be saved an need to creet out line befor savine you can try it