Signed up just to reply and confirm I'm seeing the same (sorry, I don't speak German). This is obviously a bug.
My machines are Windows 8.1 with Boxcryptor 2.1.401.69 (latest as of this post). I'm seeing the issue on 2 separate machines with pretty much identical software configurations.
Approx. every 10 seconds or so, Boxcryptor.exe creates a zero byte temp file in C:\Users\<username>\AppData\Local\Temp\. You can watch this in realtime with Sysinternals Process Monitor by filtering on the above path. The temp filenames are in the convention of "tmp*.tmp" (filenames are named between "tmp1.tmp" to "tmpFFFF.tmp" and anything in between). Presumably, Boxcryptor.exe is calling the following .NET API:
This method creates a temporary file with a .TMP file extension. The temporary file is created within the user’s temporary folder, which is the path returned by the GetTempPath method.
The GetTempFileName method will raise an IOException if it is used to create more than 65535 files without deleting previous temporary files.
The GetTempFileName method will raise an IOException if no unique temporary file name is available. To resolve this error, delete all unneeded temporary files.
The API's limitation of 65535 possible unique temp files combined with Boxcryptor's erroneous use of them (at least delete them when you're done!) is quite a big problem. When you have all 65535 temp files created in your temp folder, as was in my case, other programs that also use this API could stop working as they can no longer create temp files until you manually delete the files.
For example, on my machines:
- Outlook 2013 stopped syncing with Exchnage Online
- Atlassian SourceTree would not even start
- Some 3rd party extension for Visual Studio 2013 threw an exception on startup (not sure which one)
- SQL Server Management Studio would throw a generic exception when I tried to open a query window
- Microsoft Software Center client crashed/hung on startup
- Who knows what else...
Not to be overdramatic, but this is a ticking timebomb for most users. With a machine that is on 24/7, you will get (at most) just over 7.5 days before some .NET applications could stop working. It took me the better part of a day to figure out that Boxcryptor was the culprit after most of the applications I use day-to-day stopped working.
To the Boxcryptor Windows dev team, I think I've provided a good chunk of information about this bug and what's needed to fix it. But let me know if you need any further information or if there is a better place to file this.
Please (please!), fix this ASAP. While it's only a minor inconvenience to clear my temp folders every few days now that I know what the problem is, other users that see this problem might not know what is going on and waste a lot of time running malware scans, re-imaging machines, etc. or otherwise spending time to troubleshoot. Hopefully others find this post, at least.
Thanks for the awesome product, BTW. $48/year is really a no-brainer for what Boxcryptor provides.