Unity 5 complains "Failed to load font from memory"

I recently installed Unity 5 and ported my old projects with ease. After a while developing, one day I started getting two errors on project load:

Excerpt from Editor.log

 Failed to load font from memory
 UnityEngine.AssetBundle:LoadAsset_Internal(String, Type)
 UnityEngine.AssetBundle:LoadAsset(String, Type) (at        C:\buildslave\unity\build\artifacts\generated\common\runtime\AssetBundleBindings.gen.cs:136)
 UnityEditor.EditorGUIUtility:Load(String, Type) (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorGUIUtility.gen.cs:438)
 UnityEditor.EditorGUIUtility:LoadRequired(String) (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorGUIUtility.gen.cs:419)
 UnityEditor.Handles:Init() (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorHandles.gen.cs:721)
 UnityEditor.HandleUtility:BeginHandles() (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorHandlesUtility.gen.cs:303)

And the immediately:

 m_DirectReadCommands.status == AsyncReadCommand::kCompleted ||     m_DirectReadCommands.status == AsyncReadCommand::kNotUsed
 UnityEngine.AssetBundle:LoadAsset_Internal(String, Type)
 UnityEngine.AssetBundle:LoadAsset(String, Type) (at C:\buildslave\unity\build\artifacts\generated\common\runtime\AssetBundleBindings.gen.cs:136)
 UnityEditor.EditorGUIUtility:Load(String, Type) (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorGUIUtility.gen.cs:438)
 UnityEditor.EditorGUIUtility:LoadRequired(String) (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorGUIUtility.gen.cs:419)
 UnityEditor.Handles:Init() (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorHandles.gen.cs:721)
 UnityEditor.HandleUtility:BeginHandles() (at C:\buildslave\unity\build\artifacts\generated\common\editor\EditorHandlesUtility.gen.cs:303)

These errors have rendered my projects unusable, since Unity freezes completely, but doesn't ever say Not responding, its just frozen. When I create new projects, it still launches both errors, but it doesn't freeze, so I can start working from scratch, and these new projects do reopen, however I haven't tried simply pasting everything from and old project and see if it works.

In any case, I get the same errors every time I open Unity, either with an old or a new project, and it takes a lot of time to load, even for completely new projects. On my older, more complex projects I've noticed that two processes named UnityShaderCompiler stay hanged for a long time with zero CPU cost at the Task Manager.

My development and target platform is Windows 7. I have the free version of Unity 5.0.0f4 (64 bits).