What steps will reproduce the problem?
1. Create a "Dynamic Web Projet" 
2. Get the tag sources from Svn Trunk and Deploy on a Weblogic Server 10.0
3. With Firefox, use the following url :
http://localhost:7001/ExtTldBasic/index.jsp

What is the expected output? What do you see instead?
View the widget as I view it when I use Tomcat 6.0

Instead the following error occurs :
javax.servlet.jsp.JspException: java.lang.NoClassDefFoundError:
jsp_servlet/_tags/_ext/__panel_tag
	at jsp_servlet.__index$JspFragmentHelper.invoke(__index.java:756)
	at jsp_servlet._tags._ext.__viewport_tag.doTag(__viewport_tag.java:604)
	at jsp_servlet.__index$JspFragmentHelper.invoke0(__index.java:200)
	at jsp_servlet.__index$JspFragmentHelper.invoke(__index.java:717)
	at jsp_servlet._tags._ext.__body_tag.doTag(__body_tag.java:424)
	at jsp_servlet.__index._jspService(__index.java:146)
	at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
	at
weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:226)
	at
weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:124)
	at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:283)
	at
weblogic.servlet.internal.ServletStubImpl.onAddToMapException(ServletStubImpl.java:394)
	at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:309)
	at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:175)
	at
weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3395)
	at
weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
	at weblogic.security.service.SecurityManager.runAs(Unknown Source)
	at
weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2140)
	at
weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2046)
	at
weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1366)
	at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200)
	at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)
Caused by: java.lang.NoClassDefFoundError: jsp_servlet/_tags/_ext/__panel_tag
	at jsp_servlet.__index$JspFragmentHelper.invoke1(__index.java:208)
	at jsp_servlet.__index$JspFragmentHelper.invoke(__index.java:720)
	... 20 more  

What version of the product are you using? On what operating system?
Bea Weblogic 10.0, Bea Workshop 10.0, Firefox 2.0

Please provide any additional information below.
The tags are compiled.
In the file jsp_servlet/_tags/_ext there are :
__body_tag.class 31Ko
__panel_tag.class 145 Ko
__tabpanel_tag.class 162Ko
__toolbar_46_button_tag.class 70Ko
__toolbar_tag.class 55Ko
__tree_46_treenode_tag.class 49Ko
__tree_46_treepanel_tag.class 177Ko
__viewport_tag.class 67Ko

I made some tests and the error occurs only with the files *tag.class with
size over 100Ko