Firefox 38 beta 7 parsing problem

I have installed Firefox 38 beta 7.  It seems to be working well for
almost everything I have tried.  When invoking Firefox from my mail
reader (MR2ICE), I get an error "File not found".  With my current
version of Firefox 31.8. the address line reads
'file:///g:/tmp/mail.htm'.  With Firefox 38 beta 7, the address line
reads 'file:///g://tmp//mail.htm'.This appears to be a change in
parsing the command line parameters from earlier versions of Firefox. 
Is there a setting or change to about:config that addresses this, or is
this a bug?

Ron