Are you running a 64 bit version of Gimp ? Cos at 20 layers and maybe some hidden undo buffers perhaps its getting close to the 3-4Gb limit of 32bit apps. If it were me, id run up the sysinternals process viewer and see how much memory and how many handles etc its burning with that map open. You can look at the pagefile delta and see if its spending all its time page file thrashing too. Well, a topic for another thread but something is not quite right there. I guess being on topic tho it is worth ensuring that your system is tuned up to cope with big maps if your heading into a big map job. Just seems odd to me that PS and Gimp don't handle large images very well. I thought PS had a large image mode or is that just for the file save options. With all the resources of Adobe, cant they figure it out ? What do the pro design outfits do when customer asks for a huge billboard with photos on it up close like in an expo or something ?