java.lang.NoClassDefFoundError: org/apache/catalina/startup/Bootstrap

Hello guys,
I have a ambigious issue while starting tomcat
till two days back I was able to run my application, suddenly dont know what happened but now I can not run it.
when I start tomcat from eclipse it gives error
"java.lang.NoClassDefFoundError: org/apache/catalina/startup/Bootstrap"

and Java virtual machine launcher says "Could not find main class.Program will exit."

I googled a lot but could not find a satisfying answer.
here is my environment details for reference.

Tomcat version- apache-tomcat-5.5.26
I have added this tomcat thru [File]->[New]->[Other]->[Server] menu
after adding it when I run/debug it, it throws this error and exits.
is this a missing jar problem...though I have all the jars.. catalina.jar etc in place
or a classpath,catalina_home issue?
I have cataline_home also set to install directory of tomcat,what should be classpath?

or does it have something to do with other things?
Please help me out as I am stuck up since 2 days resolving this error when my application was running fine before it.

thanks in advance,
Rohant

tomcat starts without any error if I start it externally by envoking startup.bat
gives problem only through eclipse

I met the same problem on CentOS...

Hello ...
im guessing you would have resolved this by now ...i face the same issue
from eclipse IDE (tomcat version 6 ,java version 6) ..can you help here ?

thanks!

I have seen this same error previously.

First question how did you install Tomcat?
Did you download a packaged install or build it yourself?

If you built it yourself cd to the source trunk directory.
and "ant ide-eclipse" ,
Then re-associate eclipse with the tomcat server and it should work.

If you installed from packages.
Check your bin directory. You should have a bootstrap.jar file along with 4 or five other jar files. If you don't, do a find on your machine for bootstrap.jar and move it to your bin directory. The next error you will have is tomcat-juli.jar is not found.