My actual challenge entry is only 450 MB large, but it needs more time for saving and loading than a 1,5 GB file I worked on last month. I will thoroughly check the task manager the next time I start PS. I have done this before and from my 4 GB RAM on my 64 bit machine, PS never needs more than ~ 1,9 GB. I hope I find the reason, otherwise I'll set up my PC completely new. I simply don't have the nerves to work under this slow-down-effect.