Most importantly, you have to have a structured clearinghouse conversation with this investor. Yes, the above answers cover all the financial and legal options. Now we must uncover the "pain point" of this investor - is it slow maturity of his/her ROI? Or is it a reaction to some red flag, or maybe to a slighting? Engage with them in a trust building and sharing exercise, and I am happy to talk with you more about how useful questions and your prepared answers can put this valuable person at ease till your company succeeds.