eigen() error: R Version 1.6.1 on Mac OS X (PR#2550)

Consider this matrix:

sg

X1    X2    X3    X4    X5
1 3.240 2.592 2.592 2.592 2.592
2 2.592 3.240 2.592 2.592 2.592
3 2.592 2.592 3.240 2.592 2.592
4 2.592 2.592 2.592 3.240 2.592
5 2.592 2.592 2.592 2.592 3.240

If I compute the eigenvalues of the 'sg' matrix using R Version 1.5.0
(2002-04-29) under Linux (or using Version 1.4.0  (2001-12-19) under
Solaris), I obtain:

eigen(sg)

$values
[1] 13.608  0.648  0.648  0.648  0.648

I also obtain the same eigenvalues under R Version 1.5.1  (2002-06-17) under
Mac OS X 10.2.3.

However, if I compute the eigenvalues of the 'sg' matrix using R Version
1.6.1  (2002-11-01) under Mac OS X 10.2.3, I obtain a different answer:

eigen(sg)

$values
[1] 13.123930  0.648000  0.648000  0.648000 -1.732930

det(sg)

[1] 2.399354

det(sg,method="eigenvalues")

[1] -7.312317


Thanks,
 -- Dan --