Cannot SaveAs PSD ... too large

[Anonymous]

I have developed a good workflow from Autocad 2010 to Impression 3 with finishing touches in Photoshop. I need to save my Impression files as PSD maintaining layers - I can live without Antialiasing. Most of the time I am producing A1 sheets, and recently I find I am unable to save the file because it is apparently too big to process - that is with antialiasing turned off. The bitmaps are about 3500x5000 (that is A1@150dpi).
I have a reasonably powerful workstation, with a fast processor and Quadro FX3500 graphics. The SaveAs PSD process gets to 90% in just a 3 or 4 minutes, and then bails with the error message. I have monitored CPU and memory levels and neither seem overly taxed. It is really frustrating.
Is there any way to increase the capacity of Impression 3 to deal with larger files? The only method I can use is to SaveAs several times, each time with a subset of layers, and then recombine in Photoshop. Edited by: KeithPocock7524 on Oct 4, 2009 7:23 PM