I guess the with 12.1(27b)e4 the line card still wouldn't work.
you can check this link and search for the line card "WS-X6148A-GE-TX" and you would see the IOS version required for Sup2 to support this linecard.
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/release/notes/hardware.html#wp2563113
However my suggestion would be for you to upgrade the image to 12.2(18)SXF7 at minimum for 6148A. I just did a quick check in my lab to verify this.
Hope this answers your question.
Regards,
ranraju