After researching this issue here I found the answer under the following:
Home - All Topics - Networking - Mac Net. Q_21862435.html
One of the suggestions was to do the following:
1. Allow the mac to send clear text passwords, explaind here:
2. Allow your Windows machine to accept packets that are not digitaly signed
Change this key at the server to 0
After completing these two steps our Mac user was able to connect without issue, but the next morning they ran into the same error. Upon checking the registry the setting had reverted to 1 instead of 0.
My question is this: what could be causing this to revert and how would I fix this?