For BugReportChangeProposals, which releases are affected by this bug. You should tick all releases affected by the bug.
Discussion
I'd like to expand on the above. I'm thinking along these lines:
Just check the release you found the bug in unless you know it was introduced in an earlier release (as opposed to one that has always existed), or is also found in later ones.
The only time when I think it would be appropriate for all release to be checked is for TWikiSecurityAlerts, and in that case it would be dealt with first via the TWikiSecurityMailingList and the topic would usually be created by someone on the SecurityTeam.
-- SamHasler - 14 Feb 2005