I tried updating to 3.51 and I got another error:
System.IO.DirectoryNotFoundException: Could not find a part of the path 'G:\Documents\Downloads\Staging'.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.Directory.InternalCreateDirectory(String fullPath, String path, DirectorySecurity dirSecurity)
at System.IO.Directory.CreateDirectory(String path, DirectorySecurity directorySecurity)
at PaintDotNet.Setup.InstallingPage.d__1f.MoveNext() in D:\src\pdn\paintdotnet\src\SetupFrontEnd\InstallingPage.cs:line 1060
at PaintDotNet.Threading.IterativeTask.IterativeTaskAnon.d__0.MoveNext() in D:\src\pdn\paintdotnet\src\Core\Threading\IterativeTask.cs:line 36
at PaintDotNet.Threading.IterativeTask`1.<>c__DisplayClass1.b__0() in D:\src\pdn\paintdotnet\src\Core\Threading\IterativeTask`1.cs:line 77
Here's some other info:
I did not add PDN to the Start Menu/Programs List.
PDN was installed into my USB, then later moved to this computer.
EDIT: I installed PDN manually from GetPaint.net, and it worked. Thanks.