ligation problems. Help

[Deborah Marshall]

   I am very frustrated because I haven't been able to get a 
seemingly simple blunt-end, two-way ligation to work. My vector is
6.5 kb, with two homologous repeats (the LTRs in pLXSN), and the 
insert is 3.5 kb (b-gal). I have tried transforming ligations into
HB101 and XL1Blue, but keep obtaining colonies containing either 
vector alone, or inexplicable deletions.

   What can I do to stop this? I've already tried growing transformations
at room temp, and changing concentrations of ligase, insert, vector,
etc. Has anyone out there encountered similar problems, and what 
did they do to solve it?


Thank you very much,
Deb