Generally 100% CPU usage is a good thing when you're running an intensive application. That means it will finish sooner. But we could set it at a lower priority if we're not already doing so so that it doesn't interfere as much with the user interfacing with the operating system.
However using 100% of memory and/or crashing is something totally different. Is that what's happening? Simply using 100% CPU for a while definitely shouldn't crash the program, but it may make the computer appear sluggish.
If it's a crash, it would be helpful to know what settings you ran the search with and kind of data file you were running on.