I am not sure walls are a solution to any problem...
The most obvious solution is to get a Palestinian movement advocating non violence- how to do this - well I dont pretend to know... but bombing and invading them so far has not worked out very well- I think the only hope is a respected palestinian leader taking the risk and rising to the challenge- AND an israeli government willing to accept that challenge... so far it hasnt happenned- and doesnt look likely anytime soon...