Error write to file batch_x.tmp

Question

I am trying to import products from a csv file which i exported last time, located in var/export folder. after configuring the import profiler when i click the "Run Profile in Popup" i get immediately this error.

* Starting Mage_Dataflow_Model_Convert_Parser_Csv :: parse 
* Error write to file batch_4.tmp 
* Finished profile execution.

any suggestions, i am sure this is not related to code.