Since today I'm receiving the following YSOD when saving a product.

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +14345541
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +305
   System.Linq.WhereSelectArrayIterator`2.MoveNext() +82
   System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +296
   System.Linq.Enumerable.ToList(IEnumerable`1 source) +44
   UCommerce.Web.UI.Catalog.EditProductCatalogs.View_Saving(Object sender, EntityCommandEventArgs`1 e) +484
   System.EventHandler`1.Invoke(Object sender, TEventArgs e) +0
   UCommerce.Web.UI.Catalog.EditProduct.SaveButton_Clicked(Object sender, ImageClickEventArgs e) +98
   System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e) +134
   System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument) +204
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3804

This happens for even the most simple product (not having any additional properties) when I press the save button (with or without editing fields).

I receive this message on uCommerce-for-Umbraco7-6.5.3.14350 but after updating to version uCommerce-for-Umbraco7-6.6.2.15058 the message also appeared.

As far as I can recall, I started to receive this message after switching the User language from EN-UK to EN-US, but I doubt if this is really the issue. Nothing in the pipelines has been changed from the original installation.

Additionally, when I look at the Categories tab, I see a lot of Selected items with a red cross, without text. The Available items are empty.