Hello and welcome to the forums.
First off, if you are only using the built-in Windows Firewall and Microsoft Security Essentials then turn them both back on as neither should have any impact on your ability to network. As proof of concept turn them on and test with the wired adapter, if it works then so will the wireless. If you are currently using or have in the past, have installed on your computer any other third party AntiVirus/Internet Security Suite like Symantec/Norton, McAfee, AVG, etc. and or any software firewall products like Comodo, ZoneAlarm, etc., even if you have uninstalled them please google their respective vendor specific removal/uninstaller utility and use it to be sure all remnants are gone from your computer (since the wired connection seems to work OK, I don't suspect that this is the issue)
Second open device manager
expand network adapters
select then right click the problem adapter and choose properties
Select the "Driver" tab and
click the button to "Roll Back Driver"
answer any subsequent prompts in the affirmative and reboot.
If that doesn't help, determine the manufacturer and model name, model number and revision number of your wireless adapter and use the manufacturer's website to get the latest driver available for your specific device. If you need some help with that post the information here and someone may be able to locate a driver for you. It might help if you fill out the information regarding your system specs in your user profile area of the site as well as let us know which version of Windows 7 you are using 32 or 64 bit.
No not in so far as I know. I believe if my understanding is correct that Service Pack 1 for Windows 7, was just one big rollup of all the security updates, patches and hotfixes that had come before. My suspicions were that during that or another update process you had acquired a driver update for your network adapter from Microsoft. Not generally the best source for obtaining hardware driver updates and can sometimes result in a problem.