Sounds like the permissions are "wrong" or rather the owner is. Click on the folder, press Command+i, in the "Sharing & Permissions:" section (on the bottom) and check if it shows your new user-account on the MBP as owner (first icon) and if the privileges are "Read & Write".
Probably it will show a different user as owner. You could then try to fix the permissions by running Disk Utility, selecting you OS X partition on the left and click "Repair Disk Permissions" - but maybe this won't fix it, then you have to do it using the Terminal.
Maybe someone else can elaborate on that.
Edit 2011-12-18: Ok, I'll try myself:
Something I didn't know yet but found now looking for an easy fix:
From Troubleshooting permissions issues in Mac OS X
Note: In Mac OS X 10.5 and later, while started up ("booted") from the Mac OS X 10.5 installation disc, a user's home directory permissions can be reset using the Reset Password utility.
- But in Lion they removed the option form the menu, so if you boot (holding "alt ⌥") into Recovery HD
- Wait for “Mac OS X Utilities” menu to appear, indicating that you are booted into recovery mode
- Click on the “Utilities” menu and select "Terminal"
- Type the following:
- Confirm the user account and then the password change and reboot Mac OS X 10.7 as usual with your new password
Copied from Reset a Mac OS X 10.7 Lion Password
I didn't try it myself, but hopefully this should reset/repair your home directory permissions.
Maybe even better solution using Finder in normal OS X:
- In Finder select the folder
- Press Command+i
- Expand "Sharing & Permissions" section (Unlock if necessary
- If you're not in the list of owners, press [+]
- In the upcoming list, select your new user
- Finally click the gear
3, make your new user the owner, apply to enclosed items
- and delete the old user by selecting his name from the list and clicking [-]
Easiest way, if you're not afraid of the terminal:
Assuming your new user is named harmen
sudo chown -R harmen /Users/harmen
This will make you the owner of everything inside /Users/harmen
Read more here