Having updated the BOINC Manager to 5.10.7, I went back to the BOINC website, to find that there is only a stable version of BOINC 5.8.16. Scrolling down, I find a version of BOINC 5.10.7, but for Mac OS X. I am running Windows XP, and going to the Boinc Manager>Help>About BOINC Manager... I find that it says Version 5.10.7.
How can this be?

There seems to some bug in 5.10.7 so they don´t want more users to download it.

I am using 5.10.7 on QMC without issues. Some that use it on WCG have had varied problems. I still run 5.4.11 on WCG.

Well i am running the new 5.10.7 versions as well
2 on xp pro machines and the x64 version on vista ultimate 64
After a few days a windows update occured and the systems had to boot ... well after the reboot i found the projects being corrupted, and they ended themselfs and where auto deleted by boinc.
For the x64 i was not aware that even though projects seem to be running fine they where not supported by the projects, so when i was checking my stats was missing a lot of credits.
So i lost a week or so on these projects and had to reset all because i was not being rewarded credits at all

The only projects who seem to be running fine on X64 are this 3 :
Seti@home, Riesel sieve and Leiden Classical.
The rest of the projecs fail or simply are not recognized as being a supported platform the famous amd64 ... x64 issue seems to be part of this.
So yes i think this version has a(some) bug(s) i lost 2 long running cpdn projects again for unknown reason.

5.10.13 on Vista 64 runs QMC, Seti, and Seti Beta without any hickups so far, just wish E@H, ABC, and CP would Always getting "platform windows_x86_74 not found."

The same thing happened to me. I was running 5.10.7, and everything seemed OK, though I had a couple projects crash. (I think SZTAKI and WCG.) I went to check for upgrades, and found that this version was no longer being distributed. There was a post about it somewhere on Boincstats the next day.

I upgraded to the latest 5.10.x series, which is 5.10.13. So far, I have not had any issue with this, though I understand this is still a beta version. The original post recommended going back to the 5.8.16 version.

So... I have just returned from vacation, I wrote the post above, and now I see that 5.10.13 is the release version for Windows.

Well, then, there you go.