Kazunori Yamauchi has addressed this issue via Twitter, confirming that it will be fixed in the next game update to be released on February 18th:
Be fixed in the next update.
Sorry for the inconvenience over.
RT @co2_uk: This Gran Turismo 5 Bug Can Kill Your Game
Thank you, Kazunori, for the communications and quickly addressing the issue. Until the game update is available, everyone should still check their game save file to insure they will not be affected by the bug before then.