Did you try this??
1. Download stock iOS 5.1.1 IPSW.
2. Download redsn0w 0.9.15b2
3. Run redsn0w as administrator in windows.
4. Click Extras button.
5. Click SHSH blobs button.
6. Click Query button to see what blobs Cydia has for device.
7. If Cydia has required blobs, Click Stitch button.
8. Click IPSW button-browse for downloaded 5.1.1 IPSW file.
9. Click Blobs-Cydia button to stitch remote Cydia stored blobs to IPSW.(or could do local if you have
them local).
10. Let Process and finish. It will take a few minutes.
11. Click Back button-Click Pwned DFU to put in pwned DFU mode-follow onscreen instructions.
12. Once in pwned DFU mode, close redsn0w, launch iTunes.
13. iTunes will see device in "recovery" mode. Click Check button.
14. Hold down Shift key, click Restore button. Browse to that stitched IPSW file
you created.Select it.
15.Wait for restore to finish as normal. JB as normal(or not)...Enjoy!