>It looks like the smallest font it will accept is 8
Depends on the fonmt that you are using
>Is there any solution to this problem
See above ...
Basically, a number of the system fonts supplied with windows are what we call bitmap fonts. Basically these are pre-realised pictures of the various letters, and as a result there are only a few specific sizes available in the font. The default font used by VB controls (MS Sans Serif) is one such bimapped font, and the smallest available size is indeed 8 points (such fonts also have a maximum size).
What you need to do is select a scaleable font (either a TrueType font or an OpenType font - these are respectively indicated by a TT or O icon next to them in the font selection dialog) with which you can more-or-less select any size font you like.
However, fonts displayed at 6 points or less are often difficult to read on smaller screens, even if the font, e.g. verdana or tahoma (both reasopnable substitutions for MS Sans Serif), is designed for screen use. So you might want to revert to a bitmapped font called Small Fonts which just has as the name suggests a few small sizes available (2,3,4,5,6 and 7 point)
Having said all that, if you have a form that is so large and has so many textboxes that you need to be considering 6 point or less font size ... well, perhaps you should consider a redesign to your interface