The latest beta is mIRC v7.39, released on January 28th 2015. It can be downloaded here
and includes the following changes:
1.Extended /dll -u to allow use of a partial path.
2.Reverted Channels List window change so that modes are included in the listing again.
3.Fixed hash table bug that would have caused a crash if mIRC was unable to allocate memory for the table.
4.Fixed INI file bug where mIRC was not unloading an INI file if it no longer existed, ie. when deleted by another application.
5.Added $comchar identifier to return the command prefix character.
6.Fixed connection timeout not being applied while a STARTTLS handshake is in progress.
7.Fixed script editor bug that caused popups text not to be displayed correctly in some situations.
8.Fixed confirm exit dialog bug that was not detecting if any DCC gets were in progress.
9.Updated many routines to use 32/64-bit compatible types as a first step in preparing for a 64bit version of mIRC.
10.Fixed icon loading routine bug that may have caused an incorrect icon size to be loaded.
11.Changed threaded critical sections from InitializeCriticalSection to InitializeCriticalSectionAndSpinCount to improve performance in some contexts.
12.Fixed custom dialog limit text option not being applied to simple combo boxes.
13.Changed internal icon format for both the mIRC and connect tray icons.
14.Changed checkbox/radio button in Options/Lock/Disable features listbox and in custom dialog listboxes to use the correct Windows theme.
15.Fixed MDI windows not maximizing fully to the right in some contexts when main mIRC window is also maximized.
16.Fixed $* bug with // and other prefixes not being parsed correctly.
17.Updated file dialog routines, which includes the DCC Send file dialog, in preparation for switching to modern file dialogs in a future version.
18.Fixed /dcc send/chat/fserve bug when parsing the port number that is specified at the end of an ip address, ie. address:port.
19.Fixed Log and Buffer submenus in window system menus not being set correctly when toggling between mdi/desktop modes.
20.Fixed Shift-F3 bug under WINE that caused mIRC to freeze.
21.Extended file dialogs to include more file types in the file types listbox.
22.Fixed log reload bug that caused logs not to be reloaded before the start of a new year.
23.Added $chan(@N) wid support.
24.Added $window().idle property, returns idle state for window type.
25.Updated libraries to OpenSSL 1.0.1l.
26.Fixed while loop bug when multiple nested while loops are used on a single line separated by | line separators.
27.Fixed $reptok() bug that may have caused intermittent results.
28.Fixed $mode() bug that may have caused intermittent results.
29.Fixed empty parameter handling in $instok(), $puttok(), $remtok(), and $reptok().
30.Fixed $ini() bug that limited the index to a maximum of 9999.
31.Fixed log viewer bug that caused it to freeze during a log search if a log file contained a line longer than mIRC's maximum internal line length.
32.Fixed $mp3().bitrate bug that returned an incorrect value.