The size of the archive shouldn't matter here. What might be a problem is the number of files in the archive and the number of file file types (each file type adds its icon to the output.) Also the QL framework (or probably WebKit which is used for rendering the output) seems to leak memory. Anyway, I am aware that BetterZipQL needs to fall back on a simpler version for larger archives (no collapsable folders, etc.) The next version will handle this better.

Does the request work when you try a second time after you got this message? How many files are in your big RAR file?