I have been using lightroom 4 for a while with no problem now it wont open up and error message 0xc0000078 comes up. I have rebbooted reinstalled etc. I installed version 3 and that worked when I upgraded version 3 to 3.6 I had the same problem.
Look at my posting 95. You will see that I had same without Livid installation recently and just did the reinstal, which led to the question 'Repair Installation?', to which I simply replied 'yes'and all was fixed.