Hi,
Make sure to turn that option of for starters, to make sure to prevent that behaviour. I’m almost certain it has to do with something else as well, as there are no reports of this similar issue, I can’t see any problems on our live servers either.
Only thing I can think of is, when the plugin injects into the default search hook, it calls the default search function when IE8 string is found, and then maybe there is something executing that same hook again and it gets into the endless loop.
I tested this on our local servers by changing the conditions, but it seemed all right.