Thanks fkeel,
Tomorrow i will take some pictures to show the connector and the sensors.
In really, i have more than those sensors. My project include: LDR, TSL235R, QR1114, SH15. All of them have wires (independant ribbon cable for each sensor) , and codes what runs perfectly each one of them, but also when they are connected to arduino duemilanove.
The problem started when i removed the ribbon cables and connected all the sensor to a unique cable (8-wires). All the combinations runs ok, except when the QR1114 and the TSL235R are connected at the same time. So the problem seems to be in some way of coupling, but also when the 8-wire cable have individual shields for each couple of cables!...
The webpage where i have the description of the project is this one:
http://ardudrop.jottit.com/
however, it does not include all the information about the sensors and problems that i report here.
Here is described these two sensors (sorry, in spanish, but you can see the diagrams and the complete arduino code):
http://www.uax.es/publicaciones/archivos/TECMAD11_001.pdf
Tomorrow i will try to have more information to post here.