Hmm, you should not have downgraded the firmware, v3.04 is a good firmware version. If you lost signal, it just shows that you had a weak signal before and could do with a boost.
If you are using a laptop to connect to the dap-1360 buy a TP-Link 5dbi externa antenna and install that on the d-link unit. Will give you better coverage, even the weaker signal from the laptop to the dap-1360 will benefit from this, as the unit will pick up the weaker signal easy, because of a larger antenna.
Anyway as a side note.
Upgrading firmware should not matter as the power output from the units WIFI should is the same.