Starting today, I've been receiving lots of thees Google 403 forbidden errors while trying to navigate my AdWords account in Internet Explorer. It works fine in Firefox:

We're sorry...

... but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can't process your request right now.
We'll restore your access as quickly as possible, so try again soon. In the meantime, if you suspect that your computer or network has been infected, you might want to run a virus checker or spyware remover to make sure that your systems are free of viruses and other spurious software.
We apologize for the inconvenience, and hope we'll see you again on Google.

Anyone else have similar issues?

This may be because of below reason!

Check after you clean the temp files :)

Use the below command in your comand prompt and check again!

ipconfig /flushdns