I can confirm this 10,000 GDI objects limit for me too.
In my case I'm cleaning out unwanted images and am going through folders in Library mode marking images as rejected prior to selecting all the rejected images for deletion from disk.
GDI Objects climb as I go through hitting 'x' and as soon as it reaches 10,000 Lightroom 5.5 crashes.
Using Windows 7 64-bit, 64-bit version of Lightroom 5.5