Hi Mamatha,
Please note that workflow doesn't really need any undefined steps. If the workflow is in syntax error , then definately you need to correct the definition. You can see workflow menus ( i forgot it is edit for some other ) , you will find "Block Correction". You need to select number of nodes , i suggest whole workflow design and then do the block correction. It will correct this node problem and then you can activate the workflow.
The other solution will be go back to previous version and do your changes again , but the block correction will definately solve your problem.
Thanks
Rakesh