Interesting VACUUM notice

I found a message I've never seen before in VACUUM, its:
NOTICE:  Too old parent tuple found - can't continue repair_frag

The version is Postgresql 7.2.1.

The problem occurs in vacuum.c, around line 1700, but the interesting part is the comment around:
/*
* Read above about cases when
* !ItemIdIsUsed(Citemid) (child item is
* removed)... Due to the fact that at the moment
* we don't remove unuseful part of update-chain,
* it's possible to get too old parent row here.
* Like as in the case which caused this problem,
* we stop shrinking here. I could try to find
* real parent row but want not to do it because
* of real solution will be implemented anyway,
* latter, and we are too close to 6.5 release. -
* vadim 06/11/99
*/

This sounds like a solution should be available, but it seems to happen anyway. Yesterday I've found no way to fix this
problem,
but today it's not reproduceable any more. Might this notice indicate a serious problem?

Best regards,Mario Weilguni