WDSc Error - "Unable to create part: index.html"

Hi,
Since yesterday I have encountering the following error when I start WDSc
5.01 and try to open a html file I was working with.
 "Unable to create part: index.html". After answering the error prompts a
blank editor appears with the text
"An error has occurred when creating this editor"

So far I have tried the following without success.
-Tried closing and re-opening the project
-Renaming the workspace folder -so it might re-create any corrupted files.
-renaming the html files.

The error log has the following info:
----------------------------------------------------------
!ENTRY org.eclipse.ui 4 2 Jan 29, 2004 11:28:24.69
!MESSAGE Problems occurred when invoking code from plug-in:
"org.eclipse.ui".
!STACK 0
java.lang.NullPointerException
      at
com.ibm.etools.webedit.editor.HTMLDesignPage.dispose(HTMLDesignPage.java:329)
      at
com.ibm.etools.webedit.editor.HTMLEditor.dispose(HTMLEditor.java:972
----------------------------------------------------------

It seems to be an bug in the software that has corrupted the settings for
the project.
Wonder if anyone has encountered this problem ?  Any pointers towards
resolving this will be much appreciated.

Thank you in advance
Ruwan