I've just checked, and on my CRT yes, the vanilla EPG and Archive displays do have a slight flicker - but they are on the yellow portion of the form header or banner
only. This must be down to the design of these specific forms. It is only visible on vanilla Toppy screens - and only on that topmost part.
I have my settings at RGB and PAL I; however, having played with it, nothing makes a difference. I just assumed that this wouldn't manifest itself on flat panel TVs (LCD, plasma). What do you have?
To be honest, because I very rarely look at the standard screens, and otherwise the overall PQ is truly excellent, I had completely forgotten about it to the extent that I thought it had gone away till you mentioned it.
TAPs may not address this specific issue, but they do offer alternative EPGs. If I were you, before I sent it back for this reason, I would try installing a TAP such as MyStuff with eit2mei to see if you're happier with that, it's easy to do. A simpler alternative is EPG Navigator.
See
http://www.bobdsmystuff.co.uk/cgi/SkinLibrary.cgi for the various 'Skins' available for MyStuff, to see what you might get. The team behind it are also about to release a new version (end of year) with an overhauled EPG; and the functionality built into both the current and the next version is quite impressive, offering things you will never get with any other PVR of a similar price (bar the TiVo, no longer available). Check the MyStuff manual for what you can do.
Next version includes channel logos:
http://www.bobdsmystuff.co.uk/NextVersion_EPG.shtml
I have also read this thread contribution on toppy.org.uk (I see you have been there too with this post!):
"The default toppy OSD screens are so badly designed with respect to the colours and font choice that they do tend to flicker.
"Many of the TAPs that replace OSD screens use a a better font and have a higher font colour to background colour contrast ratio."
So I would encourage you to try an alternative EPG.
Hope this helps
Ian