Dates are irrelevant... They can be touched during the installation or the packaging (depending on how the packager and installer work). File length would be more relevant but only a 'diff' (byte per byte comparison of the two files) could tell for sure if the binaries are different or not.
I asked you to check with Snowglobe because the Cool VL Viewer is based off it and uses the same SLVoice client and an only slightly modified voice client glue code, viewer side. Comparing with another viewer is pretty irrelevant...
No. The newer SLVoice clients would require changes to the viewer code to be successfully used with it. I'll perhaps port those changes in the future, but it's pretty low on my priority list (at least for as long as voice keeps working with the old SLVoice client).
Yes, its seems to be a race condition that occurs at login, between the voice client glue code and the voice code in the IM panel (which deals with the voice UI).
For now, I implemented a workaround (a small hack) to ensure the UI and the internal voice status are synced properly after login, but to find and fix the true bug (the race condition), I would need to know what Cool VL Viewer release broke it... Next time, please do report the bug as soon as you notice it (instead for waiting for me to notice it myself: I might not be using the broken feature, which is the case for voice), because it helps tremendously to spot what went wrong and where.
The workaround will be in v1.26.4.16. In the mean time, you can simply disable and reenable voice after login (in "Preferences" -> "Voice Chat", uncheck "Enable voice chat", press the "Apply" button, then check back "Enable voice chat" and close the panel with "OK") to get things synced right for the rest of the session.