Hi Tim, as Phani suspects, when you create an account, by design, the name is a constant that is forced to stay unchanged and, for this reason, it greyes out in order to prevent conflicts with other accounts. The name of the account must be unique, in fact it is no possible to create a new account with an existing name (Create button is greyed out if so).
What options do yo have? Within what is supported and documented officially the only option you have is to create a new account and delete the old one.
If this matter is heavily impacting your operations there is an option you want might want to test. I have tested this on a lab and, at a first look, it doesn't seem to have negative or any implication at all. However, please consider the following workaround is NOT supported and NOT recommended by CA. It is my personal suggestion and possible application is at your own risk.
The accounts are stored in the CM_ACCOUNT tables. Accounts correlate with the CM_CONTACT tables (where the Account/contacts are stored) by the account_id - and not the 'name' field. Although the 'name' field is locked by the portlet not to be updated after creation, seems to be a "static" information and it does not correlated with any other table directly. Updating the name manually in the database may not be an issue [not officially tested by CA - someone correct me if i'm wrong].
Considering this is NOT supported and at your own risk, you may want to test it on a test environment with a test account and see how it goes - after ensuring you have a backup of your database. (I have tested it and I see no problems - for now )
This is the query I used to update the name of an account:
update cm_account set name = '<New_account_name>' where account_id = '<Account_id>'