Out of memory

[fg]

I've installed version 5.3.1 and I'm working with a 450 MB XML File.
I 'm working with "find" and "mark all" and I want to paste the "marked lines" in a new document, but I got the following Error-Message

out of memory. undo stack emptied. close some files and/or applications.
My Notebook has 3 GB Memory and enough free space on HDD.

Is there any workaround to fix this problem.
Thanx in advance.

[ACRobin]

One solution:
Once you have book marked all the lines you want, invert your selection (Search -> Invert bookmarks)
Delete book marked lines (edit -> delete -> book marked lines)
Save As.