System.Runtime.InteropServices.ExternalException: GDI+ is not properly initialized (internal GDI+ error) - SharePoint 2010

IIS reset fixes this issue temporarily.

Microsoft has a hotfix for this. http://support.microsoft.com/kb/975410/ 

It applies to: 
Microsoft ASP.NET 2.0
Microsoft .NET Framework 2.0 Service Pack 2

The hotfix would replace the following file with the following attributes. For all supported x86-based version and x64-based versions of the .NET Framework 2.0 in Windows 7 or in Windows Server 2008 R2

File name                       File version           File size       Date               Time  Platform
System.drawing.dll       2.0.50727.5652      626,688      11-Feb-2011   23:31  x86