Hi Sebastian,
I do use the invariant provider.
This is likely the reason for the change of behaviour then - VS2008 didn't have support for .NET 4.0 and VS2010 does. Are you sure that your VS2010 compiler is set to the .NET 3.5 compiler for your project, if the rest of your project references .NET 3.5?
If you are compiling with .NET 4.0, we will find the .NET 4.0 machine.config information, which will point to the v4.0 SQL Anywhere provider.
Regards,
Jeff Albion
SAP Active Global Support