xmlrpc() error: (-1001) unable to parse URL during Drush command
Turns out the issue was the APC module. After some testing I was able to isolate the issue during cache clear.

[shawnconn@host www]$ drush cc all
'all' cache was cleared.                                                                                                                                                                                                                                 [success]
xmlrpc() error: (-1001) unable to parse URL                                                                                                                                                                                                              [error]
[shawnconn@host www]$ drush dis apc
The following extensions will be disabled: apc
Do you really want to continue? (y/n): y
apc was disabled successfully.                                                                                                                                                                                                                           [ok]
You need to enable the APC module for remote cache clearing to work. Run drush pm-enable apc.                                                                                                                                                            [error]
[shawnconn@host www]$ drush cc all
'all' cache was cleared.                                                                                                                                                                                                                                 [success]
[shawnconn@host www]$