According to http://office.microsoft.com/en-us/starter-help/word-features-that-are-not-fully-supported-in-word-starter-HA010374498.aspx, "You can display the Quick Access Toolbar above or below the ribbon, but you cannot add or remove commands from it." The Starter
edition also can't run macros, which would be another way to turn off gridlines in the standard edition.
I think the only way to fix this may be to locate the Normal.dotm template and delete it, letting Word build a new one from the defaults.
And one more annoyance: I don't know of any MVPs who have a copy of the Starter edition to check these things. It's available only through computer vendors who load it onto new PCs, and I'm not about to buy a new PC just to get a look at Starter.