"With either the Roman Catholic understanding of character or the Orthodox understanding of the creation of a permanent hindrance due to sin, "reordination" is impossible. Even in cases when a Roman Catholic cleric may lose clerical status either through cause or petition, the sacred Ordination never becomes invalid. For both Orthodox Christians and Roman Catholics, when a member of the clergy who has been ordained in a church that shares with them an understanding of the Priesthood and by a Bishop in an unquestionable apostolic succession is received into either the Orthodox or the Roman Catholic Church, his ordination should be recognized. It should be noted, however, that until such time when the practice of the Orthodox Church will be unified, these cases will be decided by each Autocephalous Orthodox Church."
From a statement made by SCOBA in 1988.http://www.scoba.us/resources/orthodox-catholic-bishops/1988ordination.html
Also, from the OCA website:
"What is the current view of the OCA on the validity of Roman Catholic orders?
Concerning Roman Catholic orders: Within the OCA Roman Catholic clergy generally are received into the Orthodox Church through “vesting”; that is, they are not ordained anew. While there are some Orthodox Christians today who would not follow this practice, there is evidence that this was in fact the practice in Russia several centuries ago. One must also keep in mind that the practice of the Orthodox Church on this issue has been subject to change from time to time and place to place, often depending on situations appropriate to the setting."http://oca.org/questions/romancatholicism/validity-of-roman-catholic-orders
So, the answer to your question is Catholic orders may be valid or not. It depends on who you ask.