I'm trying to upgrade to 10.10 from 10.04 LTS using a custom sources.list file that points to an unofficial mirror*. The mirror does have maverick, but I get the following output when upgrading:

boatzart@somecomputer: > sudo do-release-upgrade
Checking for a new ubuntu release
Done Upgrade tool signature
Done Upgrade tool
Done downloading            
extracting 'maverick.tar.gz'
authenticate 'maverick.tar.gz' against 'maverick.tar.gz.gpg' 
tar: Removing leading `/' from member names

Reading cache

Checking package manager
Reading package lists... Done
Building dependency tree        
Reading state information... Done
Building data structures... Done 
Reading package lists... Done    
Building dependency tree          
Reading state information... Done
Building data structures... Done 

Updating repository information
WARNING: Failed to read mirror file

No valid mirror found 

While scanning your repository information no mirror entry for the 
upgrade was found. This can happen if you run a internal mirror or if 
the mirror information is out of date. 

Do you want to rewrite your 'sources.list' file anyway? If you choose 
'Yes' here it will update all 'lucid' to 'maverick' entries. 
If you select 'No' the upgrade will cancel. 

Continue [yN] y
 WARNING: Failed to read mirror file
96% [Working] 
Checking package manager
Reading package lists... Done    
Building dependency tree          
Reading state information... Done
Building data structures... Done 

Calculating the changes

Calculating the changes

Could not calculate the upgrade 

An unresolvable problem occurred while calculating the upgrade: 
The package 'update-manager-kde' is marked for removal but it is in 
the removal blacklist. 

This can be caused by: 
* Upgrading to a pre-release version of Ubuntu 
* Running the current pre-release version of Ubuntu 
* Unofficial software packages not provided by Ubuntu 

If none of this applies, then please report this bug against the 
'update-manager' package and include the files in 
/var/log/dist-upgrade/ in the bug report. 


Restoring original system state

Aborting
Reading package lists... Done    
Building dependency tree          
Reading state information... Done
Building data structures... Done 

Here is the relevant section from /var/log/dist-upgrade/main.log:

2010-11-18 14:05:52,117 DEBUG The package 'update-manager-kde' is marked for removal but it's in the removal blacklist
2010-11-18 14:05:52,136 ERROR Dist-upgrade failed: 'The package 'update-manager-kde' is marked for removal but it is in the removal blacklist.'
2010-11-18 14:05:52,136 DEBUG abort called

*I'm located inside of USC, and for some crazy reason any sustained downloads to anywhere outside of the University are throttled down to 5kbps inside of my lab. Because of this I need to use the following sources.list:

deb http://mirrors.usc.edu/pub/linux/distributions/ubuntu/ lucid main restricted universe multiverse
deb http://mirrors.usc.edu/pub/linux/distributions/ubuntu/ lucid-updates main restricted universe multiverse
deb http://mirrors.usc.edu/pub/linux/distributions/ubuntu/ lucid-backports main restricted universe multiverse
deb http://mirrors.usc.edu/pub/linux/distributions/ubuntu/ lucid-security main restricted universe multiverse

I've tried adding four more entries to the sources.list with s/lucid/maverick/ but that didn't help.

Does anyone know how to fix this? Thanks!