Visio font tracking problem when converted to .png or .vsd

[Tony Maries]

I have been editing a document which contains a large number (1000+) Visio
flow charts.
Many text boxes contain normal text, followed by a word in bold then
followed by normal text. When I convert the .vsd file to .png or .gif the
white space between the bold text and accompanying normal is often (but not
always) compressed, sometimes to zero.
The converted .vsd files are imported into FrameMaker which is then
converted to an XML file for web distribution, so I need a web-friendly
format rather than .emf, which normally produces satisfactory results when
imported into FrameMaker.
My program is Visio 2000.
The font used is Arial. I tried changing the font to Verdana and got the
same result.
I have also tried changing the resolution from the default (screen) to 300
pels and even 600 pels, which results in a fuzzy and hard to read screen
display.
The problem does definitely seem to be with the Visio program rather than
FrameMaker as the .pngs viewed in a graphics program such as Paint Shop Pro
look the same as they do in FrameMaker, with uneven spacing.