I opened an Electrum Dash wallet (2.4.1) to store some dash temporarily. Everything went normally until I went to retrieve the dash and got this message:
error: Your client produced a transaction that is not accepted by the Bitcoin network any more. Please upgrade to Electrum 2.5.1 or newer
I can't find an Electrum Dash upgrade, and really don't know what to do. 
 

 Have been using 2.0 for some time time. Downloaded and installed 2.5.4. It seems to work fine but when I close and reopen, 2.0 comes up and I have to reinstall 2.5.4 again.
This has happened repeatedly. There is only one icon in my applications file. I am running OSX 10.9.
How do I get 2.5.4 to permanently install and 2.0 to uninstall?
Thanks.