Unable to submit form from protected page

YSOD when submitting form from a protected page. Stack trace below:

[NullReferenceException: Object reference not set to an instance of an object.] Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, CacheDependency dependency) +825 Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles) +200 Umbraco.Core.Cache.DeepCloneRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles) +183 Umbraco.Forms.Core.Cache.CacheProviderExtensions.GetCacheItem(IRuntimeCacheProvider provider, String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles) +541 Umbraco.Forms.Data.StringHelper.ParseMemberPlaceholders(String value, Object memberKey) +1990 Umbraco.Forms.Data.StringHelper.ParsePlaceHolders(HttpContext context, Record record, String value) +584 Umbraco.Forms.Data.StringHelper.ParsePlaceHolders(Record record, String value) +75 Umbraco.Forms.Core.Services.WorkflowService.ExecuteWorkflows(List1 workflows, RecordEventArgs e) +1158 Umbraco.Forms.Core.Services.WorkflowService.ExecuteWorkflows(Record record, Form form, FormState state, Boolean editMode) +468 Umbraco.Forms.Web.Services.RecordService.Submit(Record record, Form form) +704 Umbraco.Forms.Web.Controllers.UmbracoFormsController.SubmitForm(Form form, FormViewModel model, Dictionary2 state, ControllerContext context) +3103 Umbraco.Forms.Web.Controllers.UmbracoFormsController.GoForward(Form form, FormViewModel model, Dictionary2 state) +339 Umbraco.Forms.Web.Controllers.UmbracoFormsController.HandleForm(FormViewModel model, Boolean captchaIsValid) +1283 lambda_method(Closure , ControllerBase , Object[] ) +167 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) +217 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) +39 System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +12 System.Web.Mvc.Async.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) +139 System.Web.Mvc.Async.AsyncInvocationWithFilters.b3d() +112 System.Web.Mvc.Async.<>cDisplayClass46.b3f() +452 System.Web.Mvc.Async.<>cDisplayClass46.b3f() +452 System.Web.Mvc.Async.<>cDisplayClass46.b3f() +452 System.Web.Mvc.Async.<>cDisplayClass46.b3f() +452 System.Web.Mvc.Async.<>cDisplayClass46.b3f() +452 System.Web.Mvc.Async.<>cDisplayClass33.b32(IAsyncResult asyncResult) +15 System.Web.Mvc.Async.<>cDisplayClass2b.b1c() +37 System.Web.Mvc.Async.<>cDisplayClass21.b1e(IAsyncResult asyncResult) +241 System.Web.Mvc.Controller.b1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +29 System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +111 System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +53 System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +19 System.Web.Mvc.MvcHandler.b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +51 System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +111 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +606 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +288