Thanks Stefan,

It's on a development server, I don't roll-out new releases to production until a point release follows as a general rule.

Im sufering that also, Im writing it here so maybe it can help something I hope, and in my events comes this with file sync active in schedule:

AssemblyVersion: -1
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider:
ExceptionGUID:
InnerException: O caminho tem um formato inválido.
FileName:
FileLineNumber: -1
FileColumnNumber: -1
Method:
StackTrace:
Message: System.ArgumentException: O caminho tem um formato inválido. em System.IO.Path.NormalizePathFast(String path, Boolean fullCheck) em System.IO.Path.GetFullPathInternal(String path) em System.IO.DirectoryInfo..ctor(String path) em DotNetNuke.Common.Utilities.FileSystemUtils.SynchronizeFolder(Int32 PortalId, String physicalPath, String relativePath, Boolean isRecursive, Boolean syncFiles, Boolean forceFolderSync) em DotNetNuke.Services.FileSystem.SynchronizeFileSystem.Synchronize() em DotNetNuke.Services.FileSystem.SynchronizeFileSystem.DoWork()
Source:
Server Name:

and this at same time:

AssemblyVersion: -1
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider:
ExceptionGUID:
InnerException: Referência de objeto não definida para uma instância de um objeto.
FileName:
FileLineNumber: -1
FileColumnNumber: -1
Method:
StackTrace:
Message: System.NullReferenceException: Referência de objeto não definida para uma instância de um objeto. em DotNetNuke.Services.FileSystem.FolderController.GetMappedDirectory(String VirtualDirectory)
Source:
Server Name:

There's a suggested fix here:

http://support.dotnetnuke.com/issue/ViewIssue.aspx?id=6709&PROJID=2