dist-upgrade error on hoary to breezy

[J. Gardner Biggs]

Preparing to replace mono-assemblies-base 1.0.5-2
(using .../mono-assemblies-bas e_1.0.5-3_all.deb) ...
Unpacking replacement mono-assemblies-base ...
dpkg: error
processing /var/cache/apt/archives/mono-assemblies-base_1.0.5-3_all.deb
(--unpack):
 trying to overwrite `/usr/lib/mono', which is also in package
libdbus-cil
Errors were encountered while processing:
 /var/cache/apt/archives/mono-assemblies-base_1.0.5-3_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

is this a known issue?

all i did was change the references to hoary to breezy in my
sources.list file.

TIA