Yeah that word caching threw me too.  Module Caching in DNN is memory based or Disk based so database caching isn't an option I don't think. 

The SiteLog can be Database or FileBased so that would make since to try switching that over if you are using Filebased.

I just discovered that I'm running into this same error tonight.  It was working yesterday, but I've been changing things trying to get other modules working and must have broken it.  I'll go back through what I changed to see if I can remedy it.

DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
InnerException: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters.
Message: DotNetNuke.Services.Exceptions.PageLoadException: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters. ---> System.IO.PathTooLongException: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters. at System.IO.Path.NormalizePathFast(String path, Boolean fullCheck) at System.IO.Path.GetFullPathInternal(String path) at System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath) at System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath) at System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList) at System.Web.InternalSecurityPermissions.PathDiscovery(String path) at System.Web.Caching.CacheDependency.Init(Boolean isPublic, String[] filenamesArg, String[] cachekeysArg, CacheDependency dependency, DateTime utcStart) at System.Web.Caching.CacheDependency..ctor(String filename, DateTime start) at System.Web.Caching.CacheDependency..ctor(String filename) at DotNetNuke.Services.Cache.FileBasedCachingProvider.FBCachingProvider.Insert(String CacheKey, Object objObject, Boolean PersistAppRestart) at DotNetNuke.Common.Utilities.DataCache.SetCache(String CacheKey, Object objObject) at DotNetNuke.Modules.Forum.DNNForum.get_Menu() at DotNetNuke.Modules.Forum.Groups.CreateChildControls() at DotNetNuke.Modules.Forum.DNNForum.CreateChildControls() at System.Web.UI.Control.EnsureChildControls() at DotNetNuke.Modules.Forum.ForumBaseControl.EnsureChildControls() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---

Are you referring to this portion of the web.config?

    <caching
      defaultProvider="FileBasedCachingProvider">
      <providers>
        <clear/>
        <add
          name="FileBasedCachingProvider"
          type="DotNetNuke.Services.Cache.FileBasedCachingProvider.FBCachingProvider, DotNetNuke.Caching.FileBasedCachingProvider"
          providerPath="~\Providers\CachingProviders\FileBasedCachingProvider\"/>
        <add
          name="BroadcastPollingCachingProvider"
          type="DotNetNuke.Services.Cache.BroadcastPollingCachingProvider.BPCachingProvider, DotNetNuke.Caching.BroadcastPollingCachingProvider"
          providerPath="~\Providers\CachingProviders\BroadcastPollingCachingProvider\"/>
      </providers>
    </caching>