Jump with Ctrl-O/I doesn't work in my Vim

I use GVim 7.2 on Windows XP. In my installation some of the jump commands don't work, such as +O 开发者_JAVA百科and Ctrl+I, whereas :jump and Ctrl+T work.

What might be the reason for this? I checked my _vimrc file for a remapping of <C-o> but there doesn't seem to be any remapping. Where should I look into to find the reason of this problem?

To get more unix-like behaviour of vim on Windows you need comment out these lines from C:\Program files\Vim\_vimrc file:

source $VIMRUNTIME/mswin.vim 
behave mswin

CTRL-O should start working after restart of vim.