Fiduciary liability is PERSONAL liability!
ERISA Section 409(a) specifies the nature of a fiduciary's liability as follows:
*Section 411 prohibits individuals convicted of various offenses from serving as a fiduciary.Any person who is a fiduciary with respect to a plan who breaches any of the responsibilities, obligations, or duties imposed upon fiduciaries by this title shall be personally liable to make good to such plan any losses to the plan resulting from each such breach, and to restore to such plan any profits of such fiduciary which have been made through use of assets of the plan by the fiduciary, and shall be subject to such other equitable or remedial relief as the court may deem appropriate, including removal of such fiduciary. A fiduciary may also be removed for a violation of section 411 of this Act.*
A fiduciary is ultimately responsible for his/her errors or omissions to the extent of having to use personal assets to restore losses and damages. In some circumstances the plan sponsor may provide some indemnification and some errors and omissions can be insured against, but generally speaking these arrangements require ultimate recourse against the individual fiduciary in order to be valid.