Error installing update 7.v2

[Firkin]

When I attempt to update my copy of FM7 Developer On OSx Panther It stops midway through the proces and reports "An unexpected error occurred while installing "554490" 1008: 17, -4". This also occurs if I try and update the trial version of FM7 that I had previously used. Any ideas as to why this should happen and what I can do about it?