ThomasH_on_the_web wrote:
1) While in LR change the catalog settings to "every time LR exits."
2) Exit LR.
3) Reenter LR.
4) Edit LR to restore the original Edit/Catalog Settings
5) Exit LR again.
As an alternative to Rafael Aviles' suggestion: A little bit more simple:
1) Change catalog backup setting to "When Lightroom next exists"
2) Exit LR, let it make the backup
3) Start LR
When LR is started again, the previous backup setting is restored, e.g. "one a month" or "never".