Ohhh I am so glad to see this thread! I have been tearing my hair out (and I dont have much..) - ever since I went to a heated bed, I've been creating lace. Works ok for a while, then goes to junk. Today I put tape back on and tried printing with a cold bed - still created lace. I suspected it might be a problem with a reduction in feed-rate, possily a heat (overheat) issue. I decided to download the latest firmware and lucked on to this post. I didnt expect to find a topic that describes my problem exactly! I'll be interested to see if someone has a solution - The short term solution will be to re-slice with a print speed that will allow me to run at 100% speed.
I am having a very similar problem. It does seem to be 'model' dependant. Some models (STL files) work, some cuse the lock-up. It doesn't seem to be dependant upon file size. Files that I opened and sliced OK in 14.03 now can be loaded. When this happens (lock-up), this is what happens: The model seems to load OK, however I cant see it untill I click on the'View Mode' icon and then 'Normal' - it usually then 'shimmers' into existance. I can rotate it, zoom in and out but as soon as I select something in the 'View Mode' (eg. 'Layers') Cura locks up.