512mb CF problems

UK:

Canon 430 Ixus

4 x 512mb CF Cards, all bought from Morgan

1 x Kingston, ok

Peak x 3 all cards, corruption probs ?

Tried the CF's in different cameras, all new cards.

For some reason, the cameras will show the JPG's ok, and in most cases
will download via cable.

However, when CF card put into either of 2 readers, none, or probs with
JPG's

Seem to be other directories, non alphanumeric characters, which
disappear when clicked on

Using imac and 10.3.9

No probs at all with Kingston, or other m'fr's cards of lower capacity.

Both cameras capable of 512mb

I've formatted, erased etc...

Ideas anyone pls

TIA