Network adaptor continually needing to be reset

I have an Acer Aspire 5755G and have had trouble recently, having changed nothing, connecting to the router on start-up. It seems to take at least a minute to do so. More annoying than this, it regularly drops out - sometimes once every few minutes, sometimes once a day or less. On most occasions I can use 'troubleshoot' and retrieve the connection as the network adaptor needs to be reset. While this is happening, the internet connection is not visible but every other broadcasting wifi in the area is still visible. The worst occasions are when there are none of the neighbours' wifi signals available as when this occurs, I get nothing from the troubleshooter as it says it can't fix it. Thus I lose things and need to reboot.
All the time the other machine that is used in the house works fine. The Acer also used to work perfectly. I've checked for other examples and found the 'power-down' suggestion in another thread but mine was not ticked so that isn't the cause or answer. Nor is the McAfee / Norton idea as I have AVG on my machine.
Does anyone have any other ideas of what to do?
Thanks!