Updating using the Update Manager fails

I've been experiencing several different failures when trying to update Views using the core Update Manager. The Update Manager has worked fine for some other modules, but is failing with both Views and at least one other module I'm using, Colorbox. In trying to sort out the problems, I've taken to just attempting one module at a time, when there are multiples with updates available.
Sometimes not all the files have gotten installed, in some instances resulting in Fatal Error bricking of the site. I've fixed this by updating the via the old FTP method I use for D6. But what's the most vexing is when there's apparent success using the Update manager and the module reports that it still needs to be updated. I'm experiencing the same issues with Colorbox, fwiw.