2. Are you using a residential address? Do you have Home Delivery setup? FedEx Rate request (I think) is the webservice being used by uStore to populate the available ship methods drop down list. Rate Request is very loose on its interpretation of Business vs Residential addresses. Leaning toward Residential.
3. What is the package you're using? I believe you cannot use a free FedEx supplied package for Ground. You have to use YOUR_PACKAGING.
4. Might be a weight limitation.
hth
~B