Thank you so much mcssschaefer!
Your hints and samples helped me, I think I am too on the right way (using PHP).
Here is the method I created for arrays (similar to normal items):
/*** Method to deal with adding arrays of elements like strings, numbers etc - only deals with homogenous array!* @param array $objects Array of the values to add.* @param String $name Name of the attribute, default value is 'name'.* @param string $type Should be either string or "number".*/public function AddArrayInput(array $objects, $name="name", $type="string") {if (empty($objects))throw new Exception("Array of objects should not be empty!", 1);$finalString = '#{';foreach ($objects as $value)$finalString = $finalString."#<$type>#<$value>#;";$finalString = trim($finalString, ";");$finalString = $finalString."}#";$attr = new stdClass();$attr->name = $name;$attr->type = "Array/$type";$attr->value = $finalString;$this->workflowInputs[] = $attr;}
When I call the workflow, I get no exceptions thrown, however, vCO still fails to validate the array parameters 
In the execution Events log (in GUI), I see this:
Workflow has failed: Invalid parameter(s)
Validation error for parameter 'alertEmailTo': OGNL error : null
And in the variables list, the Array type parameters remain "Not set"
I must be very very close! what am I doing wrong?
Here is a sample piece of the print_r of getWorkflowTokenStatus output which indicates how the parameter was constructed and passed to vCO:
stdClass::__set_state(array( 'name' => 'OrgAlertEmailTo', 'type' => 'Array/string', 'value' => '#{#<string>#<maxim@domain.com>#}#', )),
Please, any help?
EDIT: Additional information:
It seems that the validation error comes from the workflows INSIDE the workflow I am executing - for some reason either the array is not properly parsed, or not passed to the workflows inside. for example, the OrgAlertEmailTo is an input parameter for a local parameter called alertEmailTo (in Add an Organization workflow).
I am not sure what this clue means...
Message was edited by: Carmageddon