Change the default language for Eclipse User Interface

Start Eclipse with the -nl argument followed by the language en_US (for United States English) such as:
eclipse.exe -nl en_US

OR

Add the variable -Duser.language=en into the file eclipse.ini under the VMArgs section as shown below:
…
-vmargs
-Duser.language=en

“Debug certificate expired” error in Eclipse Android plugin

If a ‘clean’ on the project (go to Project -> Clean…) does not fix the error you have to delete your debug certificate under ~/.android/debug.keystore on Linux and Mac OS X resp. %USERPROFILE%/.android on Windows.

If you then build a debug package the Eclipse plugin should generate a new certificate.