c++ indentation gets messed up quite often

[sunil]

emacs : 24.1.1
GNU Emacs 24.1.1 (x86_64-redhat-linux-gnu, GTK+ Version 2.24.10) of 2012-07-13 
on x86-04.phx2.fedoraproject.org

Fedora 17
C++ mode


The indentation gets quite messed up while in the middle of editing a file.
eg: The new code will get indented to the column 0.

Usually, in the past, this has meant that i had typed something syntactically 
incorrect. Now this is not the case.
Even the tab which is set to indent shifts the line to column 0.

If I restart emacs, i can then correctly indent the line and things are back to 
normal. Bug ?

Has anyone seen this behaviour in this recent versions of emacs ?

tia,

Sunil