We faced the issue during import of solution to new organisation containing 100+ processes. Microsoft suggests to assign all workflows to the user who is going to import the solution. Refer: http://support.microsoft.com/kb/2626779/en-gb

We did not want to manually go and assign all this stuff to the new user. Hence, execute following server side code to achieve the same on target organisation:

WhoAmIRequest request = new WhoAmIRequest(); 
WhoAmIResponse response = (WhoAmIResponse)service.Execute(request); 
QueryExpression query = new QueryExpression("workflow"); 
query.Criteria.Conditions.Add(new ConditionExpression("statecode",ConditionOperator.Equal,0)); 
EntityCollection processCollection = service.RetrieveMultiple(query); 
foreach(Entity process in processCollection.Entities) 
{ 
AssignRequest assign = new AssignRequest 
{ 
//systemuser; i.e., User to whome you are assigning the entity to 
Assignee = new EntityReference("systemuser", response.UserId), 
//Current record which you are assigning to the user 
Target = new EntityReference("workflow", process.Id) 
}; 
// Execute the Request 
service.Execute(assign); 
}
 

The solution will start exporting after this without an error. Hope it helps!

Note:- You need to be System Administrator to be running this code.