* The Lazarus team recommends to use the 32bit Version of Lazarus, even for working on 64bit platforms, or for generating 64 bit applications. [1]

Current released versions of FPC (2.6.x) do not include support for SEH handling. This can affect the stability of many 64 bit applications. Therefore it is recommended to use the 32bit IDE, and generate 32bit applications only. This will change when FPC 2.8.0 is released. 
Please visit our forums and Wiki for additional information.
http://wiki.lazarus.freepascal.org/Windows_Programming_Tips#FPC_2.6.x.2FLazarus_warning_.28Missing_support_for_SEH.29