Never faced this problem before but after updating to r2 and then r3 some strange things appeared. Say, I have a mesh with several subdivision levels and sculpted details. I want to delete a part of the mesh. As usually I switch to the lowest subd level, hide unnesessary part of the mesh and click DelHidden. In previous versions when I switch to highest level - it’s ok, but now all the details are getting completely lost! Any ideas?
Neither masking of remaining part, nor using SplitHidden instead works. Moreover - I’ve figured out that SplitHidden now gives the same crappy result as DelHidden! 
Something is really wrong with it…