According to IRS Publication 946, How to Depreciate Property: when you dispose of property included in a GAA, neither the unadjusted depreciable basis, nor the depreciation reserve account of the GAA, is affected. You continue to depreciate the account as if the disposition had not occurred. The property is treated as having an adjusted basis of zero, so you cannot realize a loss on the disposition. Any amount realized on the disposition is treated as ordinary income, up to the total of the unadjusted depreciable bases of all the property in the GAA.
So the lesson is to be careful with what assets you put in the General Asset Account. Almost always create a distinct account for each depreciable asset over a given thresh hold.