[plug] Debian upt-get upgrade

[Greg]

Hello all,

I just have a simple question that has been bugging me for a while.

On my debian unstable system when i do a apt-get upgrade it states:

"The following packages have been kept back"

Followed by a list of packages.

I have had a look around but i have not been able to find a good reason
for it. If I just manaually add the packages to an install it goes through
fine.

Thanks

Greg