[RESOLVED] SQL Server permission frustration

I have a database in a SQL Server that I am the owner of. Whether I log in using Windows Authentication as myself, or log in using SQL Server authentication using the sa loggin, this problem is the same:

I can add or delete rows from a table. I can add or delete tables. I can design tables. What I can NOT do, is make even the slightest change to a table design once a table has been created. The DBA can make the changes, but if he uses my connection to the server hosting the SQL Server, then logs into SQL Server the same way he would on his computer (we are both using Remote Desktop to connect to the host), then he can't make any edits, either.

This makes it appear that it is my computer itself that is causing the trouble. The one thing we haven't tried is him remoting to the host on my computer (using his login to the host, as well as his login to SQL Server, where before, it was my login to the host, but his login to SQL Server). Other than that one, rather strange test, I would have to conclude that there is something on my computer preventing me from making edits.

The message I get when I make edits, which only happens when I attempt to save the edits, is that the changes are prevented and that the table must be dropped and re-created for the changes to be made. Naturally, this is a non-starter.

I just tested this same thing with a table that I added to the DB a couple hours back, and the same thing is happening. I simply can't make edits, even to a table that I designed and added just recently.

Any suggestions as to what is going on would be most appreciated.