When running vim under GNU screen, I'm finding that combinations of CTRL with the arrow and Pg* keys don't work as expected.
I'm using the Ubuntu 10.10
On a different machine, also running Ubuntu, this did work without problems; unfortunately I don't have that configuration available to me now.
There is a related question here: How to fix Ctrl + arrows in Vim?
However, the suggested solution there is to remap vim's keybindings to work with the terminal emulator, in that case PuTTY. I don't recall doing anything of the sort, and suspect that there is a screen configuration option which will resolve this issue.
There's also a thread on the gnu-screen mailing list which suggests that running vim via
$ TERM=xterm vim is an appropriate fix or workaround. This does work, but I'm a bit concerned that there might be side effects. It also doesn't sound familiar enough to be the solution I set up on the other machine (if a solution was necessary).