I've seen this before, whereby if the depth of your tables (i.e table within a table within a table, and so on...) is large, then the browser has a problem in handling it all, then loads fine, then doesnt, etc.
Ignore it, or use less tables 🙂
Really you should only need a maximum depth of 3 tables, maybe 4.
If it's any help, take a look at:
http://www.paule.net/
It works (generally) fine in NS4, IE4+5, and lynx, not tested with Mozilla or NS6 yet though.