Its almost as if the file has been saved in 2010 format (or earlier), rendering the new features unusable. I do keep the files on a work server, and have started password protecting my "live dwg's to eliminate that possibility.

I also considered whether importing blocks that were created in earlier versions might have something to do with it, but after a few basic tests, I have also eliminated that as being the cause.

My next theory is that it might be the recovery manger after a crash not managing to restore all the features.

Yes. It has been happening randomly since I started using 2013. Some drawings remain absolutely unaffected throughout and some get corrupted. I am currently starting again on one drawing because I opened it up 2 hours ago and, all of a sudden, I cant edit any drawing views. I'm pulling my hair out!

I am having some serious problems with the viewbase command in AutoCAD 2013 SP2. I have searched various forums for hours and I cant help but feeling that I'm on my own with it.

Since viewbase cam out, I have used it to detail the various parts from my assemblies. I use up to 25 layout tabs at a time with sometimes 10 different drawing views on each layout. Every now and then, something happens, I have no idea what, and I loose all association between the drawing views and the model. I can no longer go into the drawing views and edit hidden lines, scale etc. and if I open a new layout tab, a fresh viewbase doesn't even work. It normally happens when I re-open a drawing the day after previous session

The only work around I have, is to copy the entire model assembly into a new file or template and start again with detailing the parts.

Please help as it is wasting an unbelievable amount of my time.

Thanks in advance