tom tom suddenly slow

Hi.
I have had my Tom Tom software for ages and its worked fine on My Mio 168,
Before my latest journey I transferred TomTom onto a new 1 GB memory card,(it was on a 256 before) Now TomTom is very slow, and the map does not flow(ie the white dots in the middle of the road do not move) it seems to "stick" for about 20 seconds at a time, When approaching a manouvre the voice also stops it wil say " IN 200 YARDS......................(15 second delay)..........TURN RIGHT.

it also loses the sat signal occasionaly and the screen goes grey for 5-10 seconds.

It is like a PC programme with lack on memory.

Should the programme be on the PDA? with the Map on the storage card?
or should it all be on the card?

I reset the PDA a month ago and cannot remember whether the Programme was on the card or PDA.

Grateful for any help.