What resolution are you trying to use? Any thing above 72ppi will probably not fly. CS5.5 is only 32bit so can access only 3 GB of RAM.
Thanks for that. I found out the user was using 82ppi and advised her to lower it to 72ppi or lower. She will test and advise.
That's a physically large file -- just over 4 m x 2 m. You might find it works better in this case to export a high resolution PDF, then open that in Photoshop for conversion to JPEG.
Good call, Peter.