There are many many complaints in the Google AdWords Help forums from Internet Explorer users who are seeing errors when trying to access the billing tab within the AdWords console.
The error reads:
Error: Possible problem with your *gwt.xml module file. The compile time user agent value IE 8 does not match the run time user agent value IE 9.
Z from the Google AdWords team said this is a known issue and if you want it resolved, the steps you can take now include:
1. Clear your cache and cookies: https://support.google.com/adwords/bin/answer.py?hl=en&answer=14776
2. Set security settings: https://support.google.com/adwords/bin/answer.py?hl=en&answer=14776
3. Use a different browser, for instance you you can try free Google Chrome: https://www.google.com/chrome
There is no ETA for a fix on Google's side.
Forum discussion at Google AdWords Help.