You should always keep the previous release of any software you update, at least the time for you to verify it does not introduce severe regressions...
Also, for the Cool VL Viewer, pay attention in the release notes to the type of release and whether it is a "recommended" update or not: "recommended" releases are usually better tested for potential regressions and introduce less risky code changes or additions, while the rest is more geared towards people living on the bleeding edge. If you install the latter type, always keep the last (or last two) "recommended" release around, just in case you'd have to downgrade because of a regression...
Exceptionally, I re-uploaded the previous release (v1.26.22.35) and you can download it by copying the download URL and changing "36" for "35" in it.