Error: FAILED hr detected (hr = 0x80010102)\n / unable to update ListItem...

Hello

I'm trying to update a ListItems with a asp.net webhandler (ashx).

From an Sharepoint application Page I call the handler to update the item (jquery ajax-call). 

In the same time there might be other calls from the page in parallel (reading other items, ...).

I get the SPWeb from SPContext.

Sometimes the error

FAILED hr detected (hr = 0x80010102)\n

ErrorCode: -21474178

occurs when updating a list item. 

The same error sometings occurs too when asking for a List (Web.Lists[ListName]. When accessing the  List a second time there is no error anymore.

Is this  multithreading problem, is there a way to avoid this?

Thanks for your help

Mike