DTMF not working with IVRs and 800 numbers

I am using the PBX in a Flash distro with version of FreePBX, Asterisk and CentOS 5 kernel 2.6.18-53.1.14.el5.

I am having an issue where if I dial an 800 number that ends up in an IVR such as Google 411 I cannot get past the first level. I have contacted my SIP provider and we have done traces and what we see in the RFC 2833 RTP Event End packet is the same sequence for each of the END packets. They are telling me that these sequence errors are the problem. What is interesting is when I call into a number other than an 800 number I do not see the issue.

I have a customer that is experiencing the same issue. We have worked around this by using and temporary IAX trunk to another provider. I am not sure what else to try at this point.

and see if that works? possibly the TF vendor is messing up?

That worked, thanks. I am very surprised the vendor did not suggest that. All their documentation stated that I should use RFC 2833.