After updated OS X 10.9.5 this afternoon, I couldn't connect to Internet through wifi. Please help me!!!

Run the Network Diagnostics assistant. How far do you get?

I've been having horrible wifi connectivity problems with my mid-2012 MacBook Air for the last several weeks. I just realized today that the problems started around the time that I upgraded to 10.9.5 on September 17th.

It's reached the point where I keep Airport Utility up in a corner of my screen so I can see whether I have internet or not before hitting Send or Post.

After reading Linc Davis' post from September 27th, above, I ran the Wireless Diagnostics when I lost internet. Internet access came back while the diagnostics were running. I pressed Continue and lost connection while the second was running. Based on Airport Utility, I do not have connectivity more than I do.

Note that Airport Utility usually shows that it can see the router, but there is no Internet access. Other times it shows that it can not see the router.

Wireless Diagnostics suggested that I restart the router (a new Airport Extreme that I installed in August.) Restarted the router did not solve anything.

All other devices, wired and wireless, are working fine. The affected device is the only one running 10.9.5 wirelessly.

Any help would be greatly appreciated.

UPDATE: I reinstalled 10.9.5 and everything has been working fine since then.

am having problems HSUPA USB stick. model MF190A it is install on imac with os x 10.9.5 the strength is showing 4 bars but when i press connect for internet it is saying server is unreachable. please if there is anything i should to solve this ?