A Hamilton County judge handling the Melvin Simon estate battle has blocked Bren Simon from cashing in Simon Property Group Inc. partnership units worth more than $500 million.

Simon Property Group in January filed a lawsuit seeking guidance from the court after Bren, Melvin’s wife of 37 years, notified the company that she was electing to convert 6.5 million of the units held by her late husband.

Simon Property, which had the option of converting the units into cash or company stock, had taken the position that it should take no action because of the pending legal challenge to Melvin’s estate plan filed by his daughter Deborah.

"It would appear that the pending litigation constitutes a lien, which would not permit a conversion of the subject partnership at this time," Simon General Counsel James M. Barkley wrote in a Jan. 19 letter.

Bren had argued she could go ahead and convert the units, a position Judge William J. Hughes rejected in a ruling yesterday.

The dispute is one of several that has broken out since Deborah sued in early January, charging Bren coerced Melvin to make changes to his estate plan in February 2009, seven months before he died at age 82.

Deborah contends he was suffering from dementia and didn't understand what he was doing when he signed off on the plan, which boosted the share of his fortune going directly to Bren from one-third to one-half.

The changes also wiped out a portion that was to go to Deborah and her two siblings from Simon's first marriage—Cynthia Simon-Skjodt and David Simon, the chairman and CEO of Indianapolis-based Simon Property Group.

Bren, 66, contends the changes fully reflected Melvin’s wishes.