Just chiming in here, I get the same issue as well when using the eSearch and then trying to Print.
Also get a more detailed error when using the stock Search tool and then the Print widget.
When using the stock Search widget I get the following error in my 3.0 viewer. not trying to hijack this post, but just thought it interesting that both Search tools affect the Print tool in 3.0
**It's for a cemetery viewer...
Error executing print task:
[RPC Fault faultString="Unable to complete operation." faultCode="400" faultDetail="Error executing tool.: Layer "Locate Burial Site2": Missing or invalid 'height' in marker symbol.
Layer "Locate Burial Site2": Missing or invalid 'height' in marker symbol.
Layer "Locate Burial Site2": Missing or invalid 'height' in marker symbol.
Failed to execute (Export Web Map).
Failed to execute (Export Web Map Task)."]
I concur that the Print error only happens when either the eSearch or Search widgets are left open with selected features drawn. Once you clear selected features, or turn off the tool with features still selected, the Print for 3.0 works.