Severino allows you to upload only the first time

ARDUINO SEVERINO

Hi.
I built the ARDUINO SEVERINO SERIAL SINGLE SIDED VERSION 3 S3v3 Rev 2
I built the parallel port programmer as described at arduino home page
I have ATmega168

I burn bootload (Tools-> Burn bootloader w/Parallel Port)
and work fine, the LED starts to flash every 1 second

now connect my arduino to pc with serial cable, load any such program (eg blink), I do the upload and it works perfect, but when I try to upload for 2º time and get the error, obviously not the code.
I do not think they are the "fuses" or the "parallel programmer".
I burned the bootloader on the chip Mega168 and I test it on an arduino Duemilanove (usb) and works perfect, I've also tried the reverse, ie to burn uploader to Mega168 in the Duemilanove and then placed on the board made by hand and it is exactly the same error, can only upload a sketch for the first time.
I should also mention that I can upload the sketch with the parallel programmer without much difficulty. But the idea is that you can do with the serial connector.

Please Help...
note: please excuse the English is not my language

Since nobody has responded, I can mention that after extensive testing, I found that the problem is in the DB9, the DTR signal which is used to send a reset just before you start uploading the program is actually generated at pin 6 of the connectors.
Simply connect the pin 7 instead 4 and now can upload sketches many times without problem.
Do not know if this problem stems from some hardware motherboard.
I add a LED to DB9 pin 7 and this on/off according reset function.
I dont know is possible to short the pins 4 and 7 on the board
Sorry my bad english...