I running Lightroom 5.6. After freezing and having to force quit a number of times the exposure sliders have disappeared from the Develope Module. I have restarted LR and have relaunched both LR and OX 10.9.4 to no avail. If I run earlier LR 4 there is no problem with the exposure sliders.
I would reinstall, however LR 5.6 upgrade was a download from Abobe.