I did as you say, created first archive with about 100M of data, close, open, then adding next 100MB of date, but with adding second 100MB of data it creashed.
I have 128MB RAM.
I got strange exception(created 3 archives, 3 times happend)
This ocur only if I give new archive first(no direct add folder, and then save)
I was load about 100M of data, then I clicked save and exception ocured(uncheched backup)
System.ArgumentNullException: Value cannot be null.
I give not quit during exception, I gave continue, checked create backup, and it saved file(saved it to file l.lgp11, but If I am not wrong, its showed patch to file l.lgp).
But before, this was not happen.
Next exception, acces denied, but this I got with other program too, and I really dont know what it do. It began with work with TEX files and replacing them in lgp archives(and using preview).