AbleCommerce Shopping Cart Software

hi all, has anyone tried building the CommerceBuilder.sln from the AbleCommerceGold-GoldR5-b5731-SRC files?
I can't get it to build, errors on the new CommerceBuilder.WebApi project included in the solution.
looks like a reference problem but I can't see it.
anyone?

i'm using vs2010 and not making any changes to the files or the configuration of the solution, using exactly as downloaded.
I've also tried adding my new R5 website project to the solution and setting it as the startup project but same errors(this all worked fine with R4 src files)

thanks,
Andrew.

found error.
missing ref to system.web.routing
apologies if I troubled anyone.

I had a compile error and reported to Able this week. I never change the source code, just use it as a reference so I don't really need to compile it but I always like to check.

The compile error reported here was reproduced. We have fixed it the same way as mentioned by arawis. However we were not able to reproduce the compilation error reported separately by Judy. We have concluded that it may have to do with .NET version/configuration on the particular system.