constraint failed Error during update

Hi Everybody,

since my update to the 1.7 release I encounter regular errors caused by
svn externals. The actual error message is:

constraint failed
EXTERNALS.def_repos_relpath may not be NULL

I could figure out that the location of the repository on my hard disk
is also influencing the whole problem. The repository is regularly
located on my Desktop. At this location the error occurs. If I move the
folder to c:\ the error does not occur. Maybe the string of the path is
getting too long?
I can reproduce this error on two different machines (Windows 7 32 and
64Bit), with Version 1.7.0 and 1.7.1. If I do a fresh checkout it works
for the first time, but when I want to perform the second update I
receive the error again…

Exactly the same external is used at a different location in the
repository and works fine there.
I hope I supplied all needed information. If something is missing just
let me know.

Someone on the tortoise svn mailing List told ma the problem may be
related to SQLite. Maybe this information helps?

Thanks for your help

andre