Ah! That part of security you mean. I'm using a role that is a direct copy of Sysad role. Without any changes, so it's all full and green.
I did the trace as requested, even though I figured that wouldn't help since there doesn't seem to be a real error. Well, proved me wrong (in some way). One particular error shows up everytime this form is loaded but I can't make any peanutbutter from it (freely translated from Dutch, meaning it doesn't mean anything to me at all). Might you have any idea?
at DisplayRuleEvaluator.EvaluatePrivilegeRulePart(PrivilegeRulePart rulePart, String primaryEntity, String currentEntity) ilOffset = 0x57
at DisplayRuleEvaluator.EvaluateRulePart(RulePart rulePart, String primaryEntity, RibbonTabInformation tabInfo, DisplayRuleInformation displayRuleInformation) ilOffset = 0x2D2
at DisplayRuleEvaluator.EvaluateRule(String primaryEntity, RibbonTabInformation tabInfo, DisplayRuleInformation trimRuleInformation) ilOffset = 0x57
at RibbonDisplayRuleEvaluator.GetHiddenControls(Dictionary`2 controlMap, Dictionary`2 ruleDefinitions, String primaryEntity, DisplayRuleInformation trimRuleInformation, HashSet`1 webHiddenControls, HashSet`1 offlineHiddenControls, HashSet`1 onlineHiddenControls) ilOffset = 0x70
at RibbonDisplayRuleEvaluator.GetHiddenIds(HashSet`1 displayRuleIds, Dictionary`2 mapCommandToRule, RibbonTabInformation tabInformation, DisplayRuleInformation displayRuleInformation, HashSet`1 webHiddenControls, HashSet`1 offlineHiddenControls, HashSet`1 onlineHiddenControls, Dictionary`2 dynamicCommandDefinitions, Dictionary`2 dynamicCommandToControlMap, IOrganizationContext context) ilOffset = 0x52
at RibbonDescription.CalculateHiddenControls(DynamicMenuInformation dynamicMenuInformation, HashSet`1 currentTabCommands, RibbonTabInformation tabInformation, String entityLogicalName) ilOffset = 0x1C9
at RibbonDescription.AddCommandsForTab(String tabIdForFetch, String entityLogicalName, RibbonTabInformation tabInformation) ilOffset = 0xF0
at RibbonDescription.AddTabs() ilOffset = 0x92
at RibbonData.GetRibbonDescription(PageResourceManager currentHeader, Boolean suppressTabs) ilOffset = 0xFE
at RibbonData.CreateClientControl(PageResourceManager currentHeader, Boolean suppressTabs, EventManager parentEventManager) ilOffset = 0x7
at FormDataPage.Render(HtmlTextWriter writer) ilOffset = 0x1D6
at Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) ilOffset = 0x22
at Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) ilOffset = 0x8A4
at Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) ilOffset = 0x3C
at Page.ProcessRequest() ilOffset = 0x14
at Page.ProcessRequest(HttpContext context) ilOffset = 0x33
at CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() ilOffset = 0x18D
at HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) ilOffset = 0x15
at PipelineStepManager.ResumeSteps(Exception error) ilOffset = 0x27C
at HttpApplication.BeginProcessRequestNotification(HttpContext context, AsyncCallback cb) ilOffset = 0x31
at HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) ilOffset = 0xD3
at PipelineRuntime.ProcessRequestNotificationHelper(IntPtr rootedObjectsPointer, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags) ilOffset = 0x11E
at PipelineRuntime.ProcessRequestNotification(IntPtr rootedObjectsPointer, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags) ilOffset = 0x9
at UnsafeIISMethods.MgdIndicateCompletion(IntPtr pHandler, RequestNotificationStatus& notificationStatus) ilOffset = 0xFFFFFFFF
at UnsafeIISMethods.MgdIndicateCompletion(IntPtr pHandler, RequestNotificationStatus& notificationStatus) ilOffset = 0xFFFFFFFF
at PipelineRuntime.ProcessRequestNotificationHelper(IntPtr rootedObjectsPointer, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags) ilOffset = 0x1C8
at PipelineRuntime.ProcessRequestNotification(IntPtr rootedObjectsPointer, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags) ilOffset = 0x9
*** MSCRM:ASSERTEX *** - Unrecognized privilege depth: None