Few conflicts on 1.6, categories, products editions, alert mails.

[The-cat]

Hello and happy new year.

I look for a solution. I have no answer to the French support and worries increase. I did a migration from 1.4 to 1.6 with one click Module in October and I have several uses conflicts.

1-I have a concern with the positions of products and categories. For example, the category home is not the default category, and when I open the home category, I have all the products that appear. I have to open and close another category for home displays.
The position slider products Valid my changes but this is not always the case in customer visalisation and sometimes it changes the position of the products in the home category.

2-Some editions of products gives an error message
For example, when you change a price example was this: 2 errors
"The product must be in at least one category.
It must be in the default category "
While everything is ok on that side.

3- I performed for the first time a customer raise with a CRON task and since I do clients receive no more mail, and I no longer receive emails of purchases too. Even having re-installed the AlertMail module.
Thank you for your help.
Mary