Yes! The Solo 401k is protected against bankruptcy and creditor claims.
The passing of the Bankruptcy Abuse Prevention and Consumer Protection Act of 2005 (BAPCPA) exempts assets held in an employer-sponsored retirement plan such as a Solo 401k.
Therefore, if you file for bankruptcy, the assets held in your Solo 401k may be excluded from creditor claims.
Your funds are also protected under BAPCPA if they are being rolled from one retirement account to another. If you are in the midst of a bankruptcy proceeding, and choose to close down your Solo 401k and transfer the assets to an IRA, the funds are still protected under BAPCPA while in transit.