99 Passat tiptronic shifter not working

I have a 99 Passat that hte tiptronic shifter will not do anything.It seems to stay in automatic shifting. All the shift indicators on the display stay highlighted.
It seems to shift fine in automatic into 2nd , 3rd and 4th gears but will not go into 5th. It is also very rough when shifting from park to reverse, or neutral to drive.
Do I just need to change the transmission fluid and filter or is something else going on? any suggestions would be appreciated?

It would appear that I have stumped everyone. I can't belive that none of the experts out there have never heard of anything like this.

These shifters have magnets that control the shift selection. One of your magnets has unglued itself. If you remove the shifter you'll know what i'm talking about.
Here's a link:
http://forums.vwvortex.com/zerothread?id=3985321

Both magnets are in place. Is there anything else that could be causing it?

I started having problems with the battery not holding a charge and had to put a battery charger on it. I bought a new battery and installed it and the shifter is now working fine. I stopped by and talked to a local mechanic I've gotten to know and asked him about it. He said it made sense since a tiptronic transmission requires a higher voltage load to operate correctly than a normal transmission.

Cosmo,
You are commended for your willingness to let others know how your problem was solved. Not many here on the forum post their solutions just their problems. Thanks and glad to here your Passat is acting normal again.
Franco