Hi Sanae,
I'm not sure what's happening to cause that error message. The DBF file worked for me and successfully created the precip file. Do you have any broken data connections in the Table of Contents? When ArcMap is closed, can you check the location of the Floods_Events dbf file and make sure there are no .lock files associated with it?
If you can't get the Database option working, you can input the depths and durations from the table with the the "User-defined depth" Storm Source option in the precip form.
The can't open kin.fil error when running a simulation indicates a problem was encountered when writing the simulation inputs. Check the errors.txt file located in the folder where the MXD document is, and also open the Results window the Geoprocessing menu in ArcMap and look for any tools that didn't successfully execute during your previous sessions. Using the information there, we can probably track down what happened.
Shea