I wanted to post the crash details but, strangely, it seems totally fine now. I can't replicate it anymore.
This is making little sense.
Anyhow, keeping this confirmed for now, in case it happens to others.
Edit: Well, I deleted all .dll and .dll_patch files from the osu! folder, launched osu!.exe, and it put me on the Stable release stream.
After updating to the Beta release stream it happened again. It seems to have something to do with it being the first time you try to switch release stream in the Beta build. (This is a rushed conclusion that's more of an assumption than anything else.)
The release stream drop-down menu is empty, but the options inside are still there.
The crash happens as soon as you select an option.
Crash log seems to be a generic apphang.
Crash LogDescription:
A problem caused this program to stop interacting with Windows.
Problem signature:
Problem Event Name: AppHangB1
Application Name: osu!.exe
Application Version: 1.3.3.7
Application Timestamp: 55547e06
Hang Signature: d86f
Hang Type: 256
OS Version: 6.1.7601.2.1.0.768.3
Locale ID: 2067
Additional Hang Signature 1: d86f75197984b11a4f131e2ff9d945b8
Additional Hang Signature 2: b9af
Additional Hang Signature 3: b9afd60ebeff60354a5a5caec9ac3448
Additional Hang Signature 4: d86f
Additional Hang Signature 5: d86f75197984b11a4f131e2ff9d945b8
Additional Hang Signature 6: b9af
Additional Hang Signature 7: b9afd60ebeff60354a5a5caec9ac3448
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C:\Windows\system32\en-US\erofflps.txt
From Event Viewer 1The program osu!.exe version 1.3.3.7 stopped interacting with Windows and was closed. To see if more information about the problem is available, check the problem history in the Action Center control panel.
Process ID: 1168
Start Time: 01d08e3d8d779410
Termination Time: 55
Application Path: D:\Games\Osu!\osu!.exe
Report Id: db22a688-fa30-11e4-96c4-6c626d45738a
From Event Viewer 2- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
<Provider Name="Application Hang" />
<EventID Qualifiers="0">1002</EventID>
<Level>2</Level>
<Task>101</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2015-05-14T12:00:56.000000000Z" />
<EventRecordID>17264</EventRecordID>
<Channel>Application</Channel>
<Computer>VS-PC</Computer>
<Security />
</System>
- <EventData>
<Data>osu!.exe</Data>
<Data>1.3.3.7</Data>
<Data>1168</Data>
<Data>01d08e3d8d779410</Data>
<Data>55</Data>
<Data>D:\Games\Osu!\osu!.exe</Data>
<Data>db22a688-fa30-11e4-96c4-6c626d45738a</Data>
<Binary>55006E006B006E006F0077006E0000000000</Binary>
</EventData>
</Event>
Edit2: The "osu! configuration" (settings/recovery dialog) has an empty Release Stream dropdown menu aswell, btw.