Google Quick Search Box will freeze in OS X Lion and alloc huge memory if you input long words in search box. Only forcing to kill the QSB process could free up the memory, which makes QSB almost unusable in Lion.
After a few trials and thoughts, I found that the issue seems related to spotlight integration, which is apparently upgraded in Lion. Try to deselect spotlight results and disable spotlight plugin in QSB preference to work around it.
Works for my QSB 184.108.40.20689 and freezes no more.