I had the same problem. I went to www.justanswer.com
and asked the same question as you. I have copied my questions and answers into this reply.
My Bosch Nexxt 500 Series washer has stopped dispensing fabric
Sent to Appliance Experts 10/25/2009 at 3:24 PM
My Bosch Nexxt 500 Series washer has stopped dispensing fabric softener; I also find water in the softener dispenser cup (little cup that pops out for washing - has two sides, one for softener and the other for bleach) after every load. I have tried soaking and cleaning the cup with a brush as the manual indicates with no changes; water still standing. I removed the dispenser and filled it with water. The water didn't run out until I angled the end with the drain hole slightly down. Then the water came out through the drain hole fine. I thought maybe I hadn't cleaned it properly and bought a new dispenser assembly; this is a big part with the dispensers for detergent, softener, and bleach. I replaced my softener dispenser cup with the new one. Same problem. Help.
Make: Bosch Nexxt 500 Series
I stated my case in my question, but I did disassemble the dispenser cup. There is no blockage. It looks just like the new dispenser cup in the new assembly I bought. I also have only ran bleach through the detergent dispenser 2 times in 3 years.
Status: Awaiting Expert Reply
10/25/2009 at 3:26 PM (2 minutes and 40 seconds later)
if the dispenser is clean, then you need to replace your cold water electronic water valve. This water valve has 2 solenoids. Once for the softner and one to fill the tub. The solenoid that fills the tub can be working normally while the softner solenoid will fail to open as far as it needs and will either not send water into the softner compartment at all, or will only fill very slowly leaving diluted softner in the compartment at the end of the cycle. Here is a link to the part you need to replace. This is the part that the cold water fill hose connects to on the back of the washer.
Here is the link to the part with its description. Good luck! http://www.repairclinic.com/SSPartDetail.aspx?s=t-WFMC3301UC-%3d%3di1105556&PartID=1105556