In our current app we have quite a few custom xml files used for meta definitions. We have our own schemas defined for these xml files as to what elements are required, what attributes are required on those elements, several complex types, etc. With Visual Assist enabled the intellisense box disappears after typing the first letter of any element or attribute. Disabling Visual Assist allows the IDE to exhibit the correct behavior.
This is similar to case 921 that was addressed in build 1445. Is this the same issue rearing its ugly head in a new IDE?
Do your files have the extension XML? This sounds like a problem reported in ASAX files. The problem in ASAX files has been fixed internally, so this might be fixed in the next build. We are hoping to get a beta build posted in the next few days.
The extensions of our files vary by our usage. They are all valid xml files, but could have extensions of config, or other variations as needed by our code generator.