Error changing properties file in tomcat

I got a strange problem in Tomcat using Eclipse. I've modified some properties in weibo_config.properties file, which configure the Weibo API. However, the modified attributes remain the earlier value.

Expected result
before modification: key = OLD_KEY
after modification: key = NEW_KEY

Realty
before modification: key = OLD_KEY
after modification : key = OLD_KEY

What I've tried :

• clean the tomcat server
• remove the web app in tomcat
• restart eclipse

But it didn't work. By the way, my collegue used MyEclipse as an IDE, it works after sychornizing my properties modification. So it was rather a configuration problem.

So what should I do in order to fix this problem ?