if you're putting a space between words and at lease one of the words is REALLY common you'll get a memory error because too many results are returned.
if you search for "furry guns" which you would expect to return a limited number of results you'll get an error.
This is because the search feature is looking for either "furry" OR "guns". The word guns is so common on this forum that the result set will be to large and cause the error.
Just guessing that might be your problem. Good luck.