Update: Max has released ChronoForms v4 RC3.1 for Joomla! 1.6/1.7/2.5. Please upgrade now if you are using these Joomla! versions.
Joomla! 2.5 has now been released and there is a security update recommending that 1.6 & 1.7 users upgrade to 2.5.
ChronoForms v4 RC3.0 has a small problem with 2.5 which is easily fixed. Please see this post
for the info.
If you want to stay with Joomla! 1.7 then there is a 1.7.4 release with the security fixes available here