It sounds to me like you are using SSAS (Analysis Services). I always try to start out using the base objects as they are in the DSV, and if I need to do something special I can expend it would select statements. You should definitely just have one dimension and not try and create duplicates to be use for different measure groups. You can use the same dimension more than once in the same cube or measure group. For instance the time dimension might be used multiple times in the same measure group, once for transaction start, and once for transaction end for instance. The dimension can also be used by different measure groups or cubes. There is a concept of role playing which is how the measure group uses the dimension, or the context it uses it in. This abstraction layer allows for the contextual dimension to use a different name than the base dimension.

Hope this helps.