We are looking towards moving everything away from Foxpro and towards a new technology. Probably over 3 to 5 years. These are the layers we initially outlined:

Presentation Layer - Thin client and some thick client (browser-based, Java, C#).
Application Server Layer - Handle requests from Presentation Layer and outside sources (Java or C#).
Business Rules Layer - Interpret requests and return/update data in the Data Layer (Java or C#).
Data Layer - SQL Server or Oracle.

Any very general recommendations as to whether C# or or Java would be better choices? Is there a right and wrong combination of languages across the layers?

Looking for some very broad thoughts here.