Again, I'm not one who has ever used a homegroup, I like to do it the "old school" way using usernames and passwords, and shares.
With that being said, how are you mapping your drives? There are of course many ways to do it in Windows 7 (and I would guess Windows 8 as well).
If this is something you always want to have connected, I would go into Windows Explorer, and click on the button for "Map Network Drive". I know in Windows 7, that is option near the top of the screen.
The screen that comes up when you do that is shown above (again, from Windows 7). I would then put in the full name of the share as shown below
• \\192.168.0.1\sharename
OR
• \\mymachinename\sharename
Then, make sure the box "reconnect at login" is checked. Also, if you want to connect using a different set of credentials (which would probably be the case unless you have the same username and password on the box you are trying to connect to), check that box as well. When you do that, you will be presented with a 2nd dialog box, where you will enter in the username and password that you want to use to connect. Make sure you enter the information for that box in the following format
Username: mymachinename\username
Password: password
Or
Username: 192.168.0.1\username
Password: password
Again, while the homegroup concept is suppose to make things easier on the end user and remove all these steps, it may be worth a shot to give this a try and see if it works.
You may also want to verify how your shares are setup as well (permissions and all that), on both the share itself, and the directories in the share for the user that is connecting in.
--Brian