Cache vulnerability due to soft errors is one of the reliability concerns in embedded systems. Dynamic reconfiguration techniques are widely studied for improving cache energy without considering the implications of cache vulnerability. Maintaining a useful data longer in the cache can be beneficial for energy improvement due to reduction in miss rates, however, longer data retention negatively impacts the vulnerability due to soft errors. This paper studies the trade-off between energy efficiency improvement and reduction in cache vulnerability during cache reconfiguration. We propose two heuristic approaches for reliability- and energy-aware dynamic cache reconfiguration. Experimental results demonstrate that our proposed approaches can provide drastic reduction in cache vulnerability with minor impact on energy and performance.